Abstract: GABA_A receptors are pentameric ligand-gated ion channels (pLGICs) essential for inhibitory neurotransmission in the brain. Although their three-dimensional structures are increasingly well defined, the molecular mechanisms that couple neurotransmitter or drug binding to opening of the ion-conducting pore remain poorly understood. Here, we use both conventional and unnatural mutagenesis to demonstrate that main-chain hydrogen bonds (H-bonds) within transduction loops are crucial for transducing GABA binding to ion conduction. 

We identify an essential H-bond that couples the extracellular neurotransmitter-binding and transmembrane domains that has been conserved in inhibitory pLGICs for billions of years. Disruption of this H-bond provides a mechanistic explanation for neurological disorders including epilepsy, neurodevelopmental disability, and hyperekplexia (startle disease). These findings reveal a previously underappreciated role for main-chain chemistry in pLGIC function.

Biography: Marcel Goldschen-Ohm’s training integrates physics, biophysics and ion channel physiology. After working in high-energy physics and quantum computing, he followed a long-standing interest in neuroscience to study ion channels. He completed his Ph.D. with Mathew Jones, where he developed expertise in GABA_A receptor biophysics, patch-clamp electrophysiology and Markov modeling. As a postdoc with Baron Chanda, he developed a fluorescence-based approach for visualizing ligand binding dynamics at single molecules. At UT Austin, Marcel’s research program defines fundamental mechanisms of ion channel gating and drug modulation and its dysfunction in neurological disease.

Abstract: Learning element symbol-name relationships and the spatial organization of elements on the periodic table is a foundational step in learning chemistry, supporting later understanding of chemical formulas, equations, bonding and stoichiometry. Although students often rely on memorization strategies to learn periodic table content, this task is challenging due to the large number of elements and the apparent ambiguity in matching some element symbols to their names. 

This study explores students’ recall of element names when given element symbols as cues and their knowledge of element locations on the periodic table when given element names as cues. The study also examines how these two pieces vary across course groups. Seven instructional groups representing increasing levels of chemistry coursework were examined using two complementary but distinct experimental approaches: a survey-based cued-recall task assessing percentage-correct symbol-name recall, and a separate eye-tracking experiment assessing how students visually searched for selected elements on the periodic table.

The overall results with all elements considered together reveal that recall of element symbol-name relationships and visual search efficiency improve with increasing chemistry exposure, but do not follow a strictly stepwise progression. Element-specific analyses reveal that recall of symbol-name relationships developed unevenly across the periodic table: 

• Some elements consolidate early.
• Others strengthen gradually with increased exposure to chemistry.
• A subset remain weakly recalled even among upper-level undergraduate and graduate students. 

Visual search efficiency follows a similar pattern, shifting from exploratory search to shorter, more focused search paths in advanced course groups. Recall and visual search efficiency were similar but not equivalent. In some cases, elements were located efficiently despite weak or absent recall, whereas in others  elements recalled were associated with inefficient search behavior. 

These findings indicate that symbol-name knowledge and spatial knowledge of element locations constitute distinct but interacting memory components. At the upper levels of instruction, there seems to be an integration of these components, enabling students to use the periodic table more effectively as a structured representation rather than relying solely on element symbol-name associations.

KEYWORDS: Periodic table, symbol–name relationalships, visual search, search behavior, consolidation, integration

Abstract: Learning element symbol-name relationships and the spatial organization of elements on the periodic table is a foundational step in learning chemistry, supporting later understanding of chemical formulas, equations, bonding and stoichiometry. Although students often rely on memorization strategies to learn periodic table content, this task is challenging due to the large number of elements and the apparent ambiguity in matching some element symbols to their names. 

This study explores students’ recall of element names when given element symbols as cues and their knowledge of element locations on the periodic table when given element names as cues. The study also examines how these two pieces vary across course groups. Seven instructional groups representing increasing levels of chemistry coursework were examined using two complementary but distinct experimental approaches: a survey-based cued-recall task assessing percentage-correct symbol-name recall, and a separate eye-tracking experiment assessing how students visually searched for selected elements on the periodic table.

The overall results with all elements considered together reveal that recall of element symbol-name relationships and visual search efficiency improve with increasing chemistry exposure, but do not follow a strictly stepwise progression. Element-specific analyses reveal that recall of symbol-name relationships developed unevenly across the periodic table: 

• Some elements consolidate early.
• Others strengthen gradually with increased exposure to chemistry.
• A subset remain weakly recalled even among upper-level undergraduate and graduate students. 

Visual search efficiency follows a similar pattern, shifting from exploratory search to shorter, more focused search paths in advanced course groups. Recall and visual search efficiency were similar but not equivalent. In some cases, elements were located efficiently despite weak or absent recall, whereas in others  elements recalled were associated with inefficient search behavior. 

These findings indicate that symbol-name knowledge and spatial knowledge of element locations constitute distinct but interacting memory components. At the upper levels of instruction, there seems to be an integration of these components, enabling students to use the periodic table more effectively as a structured representation rather than relying solely on element symbol-name associations.

KEYWORDS: Periodic table, symbol–name relationalships, visual search, search behavior, consolidation, integration

Abstract: The human genome encodes approximately 20,000 proteins, of which about 85% lack well-defined druggable binding pockets, leaving most of the disease-relevant proteins “undruggable."

Small molecule chemical probes are essential for modulating protein function and serve as leads for therapeutic development. However, the majority of the human proteome remains inaccessible to conventional drug-like molecules due to the absence of suitable binding pockets. Intrinsically disordered proteins (IDPs) and intrinsically disordered regions (IDRs) represent a particularly hard-to-drug class within this undruggable proteome. Although IDPs lack stable tertiary structures, they still play central roles in transcriptional regulation, oncogenic signaling, and cellular stress responses. 

Mass spectrometry-based cysteine chemoproteomics has emerged as a promising approach to address this druggability gap by mapping cysteine reactivity across the proteome. Cysteine-thiol (Cys-SH) is the preferred nucleophile for site-selective protein modification because of its high intrinsic reactivity, low natural abundance, and regulatory significance. Nonetheless, significant challenges remain, as conventional cysteine-targeted electrophiles (warheads) predominantly modify solvent-exposed residues in well-folded protein domains, leaving IDPs and IDRs largely inaccessible to covalent targeting. Existing strategies for engaging IDPs often depend on serendipitous or cryptic pocket targeting, which do not provide a generalizable or mechanistically understood framework for capturing the disordered cysteinome.

This work spans multiple disciplines by integrating structure-guided design, chemical synthesis, analytical characterization, quantitative mass spectrometry-based chemoproteomics, computational modeling, structural data integration and cell-based validation to address these challenges. We hypothesized that cyclometalated Au(III)[C^N] frameworks bearing unconventional and tunable bulky monodentate phosphine ancillary ligands would modulate steric shielding at the gold(III) center to enable site-selective cysteine arylation within disordered protein regions. 

These gold(III) complexes form irreversible C(sp²)-heteroatom bonds via metal-mediated aryl transfer to Cys-SH, and their square-planar geometry and relativistic stabilization enhance their electrophilicity and affinity for soft nucleophiles like Cys-SH. The overall outcome is a new class of gold(III) arylating reagents with tunable ancillary ligands that covalently target cysteines within dynamically unstable IDRs, thereby increasing local protein structural stability while preserving existing disulfide bonds. Altogether, we designed a next-generation biorthogonal cyclometalated gold(III) probe platform and expanded our in-house technique, Metal-mediated Ligand Affinity Chemistry (MLAC), by conjugating protein-binding ligands to gold(III) arylating reagents for proximity-driven, site-selective covalent modification of native IDPs.

Using this platform, we demonstrated IDR-selective covalent targeting of historically undruggable proteins, including redox-sensitive Galectin-1, disordered regions of Heme Oxygenase-2 (HMOX2), and mutant KRAS G12C, achieving a "speed + IDP selectivity" profile unattainable by conventional electrophiles. We profiled the human cysteinome in triple-negative breast cancer (TNBC) cell lines through gold(III)-mediated one-pot CuAAC biorthogonal click chemistry coupled with quantitative chemoproteomics. This approach identified 391 IDPs, including 261 undruggable proteins that are not targeted by FDA-approved drugs or small molecules listed in DrugBank or ChEMBL, and deposited the complete dataset in the PRIDE proteomics repository.

However, the impact of our MLAC work will be limited if researchers cannot apply this platform in biologically relevant systems. Building on these chemoproteomic findings, we then developed gold(III) arylating reagents conjugated to Lenalidomide to selectively target cysteines coordinated to the zinc(II) metal center in Cereblon, thereby reprogramming the specificity of E3 ligases and expanding the degradable proteome. We further extended this chemistry towards therapeutic translation to engineer site-specific antibody-drug conjugates (ADCs) with enhanced homogeneity and drug-to-antibody ratio (DAR) while preserving antibody activity through cysteine-selective bioconjugation.

Collectively, this dissertation expands our understanding of the druggable cysteinome by establishing cyclometalated gold(III) chemistry as a unified framework that connects IDP targeting, quantitative chemoproteomic mapping, organometallic protein degradation, and precision bioconjugation. This work delivers structure-guided principles for gold(III) probe design and mass spectrometry-based workflows that enable covalent targeting of proteins previously considered undruggable, thereby deciphering the mechanisms underlying protein undruggability to advance covalent drug development and translational cancer therapeutics.

Abstract: The human genome encodes approximately 20,000 proteins, of which about 85% lack well-defined druggable binding pockets, leaving most of the disease-relevant proteins “undruggable."

Small molecule chemical probes are essential for modulating protein function and serve as leads for therapeutic development. However, the majority of the human proteome remains inaccessible to conventional drug-like molecules due to the absence of suitable binding pockets. Intrinsically disordered proteins (IDPs) and intrinsically disordered regions (IDRs) represent a particularly hard-to-drug class within this undruggable proteome. Although IDPs lack stable tertiary structures, they still play central roles in transcriptional regulation, oncogenic signaling, and cellular stress responses. 

Mass spectrometry-based cysteine chemoproteomics has emerged as a promising approach to address this druggability gap by mapping cysteine reactivity across the proteome. Cysteine-thiol (Cys-SH) is the preferred nucleophile for site-selective protein modification because of its high intrinsic reactivity, low natural abundance, and regulatory significance. Nonetheless, significant challenges remain, as conventional cysteine-targeted electrophiles (warheads) predominantly modify solvent-exposed residues in well-folded protein domains, leaving IDPs and IDRs largely inaccessible to covalent targeting. Existing strategies for engaging IDPs often depend on serendipitous or cryptic pocket targeting, which do not provide a generalizable or mechanistically understood framework for capturing the disordered cysteinome.

This work spans multiple disciplines by integrating structure-guided design, chemical synthesis, analytical characterization, quantitative mass spectrometry-based chemoproteomics, computational modeling, structural data integration and cell-based validation to address these challenges. We hypothesized that cyclometalated Au(III)[C^N] frameworks bearing unconventional and tunable bulky monodentate phosphine ancillary ligands would modulate steric shielding at the gold(III) center to enable site-selective cysteine arylation within disordered protein regions. 

These gold(III) complexes form irreversible C(sp²)-heteroatom bonds via metal-mediated aryl transfer to Cys-SH, and their square-planar geometry and relativistic stabilization enhance their electrophilicity and affinity for soft nucleophiles like Cys-SH. The overall outcome is a new class of gold(III) arylating reagents with tunable ancillary ligands that covalently target cysteines within dynamically unstable IDRs, thereby increasing local protein structural stability while preserving existing disulfide bonds. Altogether, we designed a next-generation biorthogonal cyclometalated gold(III) probe platform and expanded our in-house technique, Metal-mediated Ligand Affinity Chemistry (MLAC), by conjugating protein-binding ligands to gold(III) arylating reagents for proximity-driven, site-selective covalent modification of native IDPs.

Using this platform, we demonstrated IDR-selective covalent targeting of historically undruggable proteins, including redox-sensitive Galectin-1, disordered regions of Heme Oxygenase-2 (HMOX2), and mutant KRAS G12C, achieving a "speed + IDP selectivity" profile unattainable by conventional electrophiles. We profiled the human cysteinome in triple-negative breast cancer (TNBC) cell lines through gold(III)-mediated one-pot CuAAC biorthogonal click chemistry coupled with quantitative chemoproteomics. This approach identified 391 IDPs, including 261 undruggable proteins that are not targeted by FDA-approved drugs or small molecules listed in DrugBank or ChEMBL, and deposited the complete dataset in the PRIDE proteomics repository.

However, the impact of our MLAC work will be limited if researchers cannot apply this platform in biologically relevant systems. Building on these chemoproteomic findings, we then developed gold(III) arylating reagents conjugated to Lenalidomide to selectively target cysteines coordinated to the zinc(II) metal center in Cereblon, thereby reprogramming the specificity of E3 ligases and expanding the degradable proteome. We further extended this chemistry towards therapeutic translation to engineer site-specific antibody-drug conjugates (ADCs) with enhanced homogeneity and drug-to-antibody ratio (DAR) while preserving antibody activity through cysteine-selective bioconjugation.

Collectively, this dissertation expands our understanding of the druggable cysteinome by establishing cyclometalated gold(III) chemistry as a unified framework that connects IDP targeting, quantitative chemoproteomic mapping, organometallic protein degradation, and precision bioconjugation. This work delivers structure-guided principles for gold(III) probe design and mass spectrometry-based workflows that enable covalent targeting of proteins previously considered undruggable, thereby deciphering the mechanisms underlying protein undruggability to advance covalent drug development and translational cancer therapeutics.

Abstract: Master regulatory control programs coordinate genetic activity, metabolic state and stress adaptation across cellular systems. Targeting these programs remains a major challenge in chemical biology due to structural complexity, network redundancy, and context-dependent regulation. Understanding how chemical tools can reprogram interwoven regulatory layers is essential for overcoming limitations of current therapeutic strategies. 

This dissertation examines how small molecules can modulate two interconnected master regulators: the transcription factor MYC and the mitochondrion. MYC is a protein that regulates the transcription of about 15% of genes in the body, while the mitochondrion is the central organelle governing bioenergetic and redox homeostasis, both of which are frequently altered in inflammatory states.

MYC drives numerous human cancers and represents a viable yet historically intractable target due to its intrinsically disordered structure and lack of a defined binding pocket. Many MYC inhibitors fail because reversible interactions are insufficient to stabilize engagement of this unstable protein.

 To address this challenge, I developed multiple strategies to achieve functional chemical engagement of MYC. An in-house platform termed Metal-mediated Affinity Chemistry enabled proximity-guided, site-selective targeting of MYC. The known MYC-MAX disruptor 10058-F4 was conjugated to an Au(III)-based warhead capable of chemo-selective cysteine modification within intrinsically disordered regions, stabilizing small-molecule-MYC interaction and enhancing potency without reliance on conventional pocket binding.

In parallel, through the development of MY05, I established direct intracellular inhibition of MYC. MY05 selectively disrupts MYC-MAX heterodimerization and attenuates MYC-dependent transcriptional programs in cancer models, demonstrating that intrinsically disordered transcription factors can be chemically engaged with meaningful functional consequences. MY05 also provides a chemical framework for the subsequent development of potent covalent modifiers and degraders of MYC.

To extend beyond direct inhibition, complementary approaches were pursued to regulate MYC indirectly through its upstream biochemical control. Targeting HMOX2 revealed a chemical axis that promotes MYC depletion while simultaneously modulating mitochondrial function and redox balance. These findings uncover a mechanistic interface between mitochondrial metabolism and oncogenic transcription, demonstrating that bioenergetic state influences MYC-dependent gene expression. 

Chemical perturbation of mitochondrial function was shown to reprogram metabolic states and selectively challenge disease-associated phenotypes. Mitochondria thus function as regulatory nexuses capable of reshaping proliferative and inflammatory signaling networks.

Building on this intersection, direct modulation of mitochondrial regulatory programs was investigated in inflammatory contexts. A brain-penetrant Au(III)-based compound, AuPhos, induced mitochondrial biogenesis, enhanced oxidative capacity, regulated inflammatory signaling and promoted coordinated transcriptional remodeling. In a model of traumatic brain injury, mitochondrial enhancement supported molecular programs associated with metabolic resilience and tissue repair.

Collectively, this work establishes a framework for chemical reprogramming of transcriptional and bioenergetic control systems. Through small-molecule MYC engagement, redox-mediated MYC regulation, and mitochondria-driven transcriptional remodeling, these studies define the functional interplay among master regulatory layers. Further elucidation of the MYC-mitochondrial interface may enable precision modulation of cellular state and inform the development of next-generation therapeutics.

Abstract: Master regulatory control programs coordinate genetic activity, metabolic state and stress adaptation across cellular systems. Targeting these programs remains a major challenge in chemical biology due to structural complexity, network redundancy, and context-dependent regulation. Understanding how chemical tools can reprogram interwoven regulatory layers is essential for overcoming limitations of current therapeutic strategies. 

This dissertation examines how small molecules can modulate two interconnected master regulators: the transcription factor MYC and the mitochondrion. MYC is a protein that regulates the transcription of about 15% of genes in the body, while the mitochondrion is the central organelle governing bioenergetic and redox homeostasis, both of which are frequently altered in inflammatory states.

MYC drives numerous human cancers and represents a viable yet historically intractable target due to its intrinsically disordered structure and lack of a defined binding pocket. Many MYC inhibitors fail because reversible interactions are insufficient to stabilize engagement of this unstable protein.

 To address this challenge, I developed multiple strategies to achieve functional chemical engagement of MYC. An in-house platform termed Metal-mediated Affinity Chemistry enabled proximity-guided, site-selective targeting of MYC. The known MYC-MAX disruptor 10058-F4 was conjugated to an Au(III)-based warhead capable of chemo-selective cysteine modification within intrinsically disordered regions, stabilizing small-molecule-MYC interaction and enhancing potency without reliance on conventional pocket binding.

In parallel, through the development of MY05, I established direct intracellular inhibition of MYC. MY05 selectively disrupts MYC-MAX heterodimerization and attenuates MYC-dependent transcriptional programs in cancer models, demonstrating that intrinsically disordered transcription factors can be chemically engaged with meaningful functional consequences. MY05 also provides a chemical framework for the subsequent development of potent covalent modifiers and degraders of MYC.

To extend beyond direct inhibition, complementary approaches were pursued to regulate MYC indirectly through its upstream biochemical control. Targeting HMOX2 revealed a chemical axis that promotes MYC depletion while simultaneously modulating mitochondrial function and redox balance. These findings uncover a mechanistic interface between mitochondrial metabolism and oncogenic transcription, demonstrating that bioenergetic state influences MYC-dependent gene expression. 

Chemical perturbation of mitochondrial function was shown to reprogram metabolic states and selectively challenge disease-associated phenotypes. Mitochondria thus function as regulatory nexuses capable of reshaping proliferative and inflammatory signaling networks.

Building on this intersection, direct modulation of mitochondrial regulatory programs was investigated in inflammatory contexts. A brain-penetrant Au(III)-based compound, AuPhos, induced mitochondrial biogenesis, enhanced oxidative capacity, regulated inflammatory signaling and promoted coordinated transcriptional remodeling. In a model of traumatic brain injury, mitochondrial enhancement supported molecular programs associated with metabolic resilience and tissue repair.

Collectively, this work establishes a framework for chemical reprogramming of transcriptional and bioenergetic control systems. Through small-molecule MYC engagement, redox-mediated MYC regulation, and mitochondria-driven transcriptional remodeling, these studies define the functional interplay among master regulatory layers. Further elucidation of the MYC-mitochondrial interface may enable precision modulation of cellular state and inform the development of next-generation therapeutics.

Abstract: Cancer cells have developed uncanny strategies to evade the effectiveness of anticancer therapies and immune destruction by modulating their energy metabolism to a pro-survival state. This altered metabolism supports their proliferation and enables niches to thrive even in the presence of unfavorable conditions. 

The glycolytic and the mitochondrial-mediated energy generation pathways represent some of the most dysregulated energy pathways in tumorigenesis. Metabolic profiling has shown the upregulation of glycolysis, oxidative phosphorylation, and the dual dependence of most cancers on both pathways for energy, in a need-dependent manner. 

Here, I report on strategies that leverage the multiple energy pathway dependence of triple-negative breast cancer (TNBC) as a therapeutic approach; identify a novel energy metabolism-perturbing therapeutic target; and elucidate the role of endogenous and exogenous mitochondrial perturbation in breast cancer metastasis and progression. 

The excessive energy demand of the highly proliferative TNBC is a crucial driver of metabolic plasticity. I hypothesized that targeting multiple metabolic pathways in a dual-therapy approach in cancer will provide a profound exploitation of metabolic vulnerabilities for efficacious treatment regimens. Thus, I leveraged this energy gluttony to develop a strategy that targets both glycolysis and oxidative phosphorylation, using 2-deoxyglucose (2DG), a hexokinase (HK) inhibitor, and an OXPHOS-targeting gold(III) anticancer agent, respectively.

The in vivo anticancer response demonstrated improved synergy. However, the non-specificity of 2DG in targeting hexokinase led to a specific CRISPR-Cas9-mediated manipulation of HK1, HK2, and HK3 respectively in TNBC cells. Further rigorous target validation studies culminated in the identification of HK3 as a promising therapeutic target in TNBC, revealing it to be a previously uncharacterized and markedly understudied isoform. 

In efforts to glean more insights into cancer energy metabolism and the mitochondrial-modulatory potency of gold(III) complexes, I validated the antitumorigenic, antimetastatic and energy stress-inducing effects of targeting voltage-dependent anion channels 1 (VDAC1), the main regulator of metabolite flux between mitochondria and cytosol, in TNBC using various in vitro and in vivo models. 

Exogenous mitochondria transfer, a term that describes the trafficking of mitochondria from external donors to cancer cells, has gained traction as an emerging concept in cancer energy metabolism. To further our understanding of this concept, I have shown that cancer cells hijack the mitochondria of immune cells, resulting in depletion of metabolic energy available to the immune cells. This study identifies a new therapeutic target and unveils new insight into our understanding of targeting energy metabolism in cancer.

Abstract: Cancer cells have developed uncanny strategies to evade the effectiveness of anticancer therapies and immune destruction by modulating their energy metabolism to a pro-survival state. This altered metabolism supports their proliferation and enables niches to thrive even in the presence of unfavorable conditions. 

The glycolytic and the mitochondrial-mediated energy generation pathways represent some of the most dysregulated energy pathways in tumorigenesis. Metabolic profiling has shown the upregulation of glycolysis, oxidative phosphorylation, and the dual dependence of most cancers on both pathways for energy, in a need-dependent manner. 

Here, I report on strategies that leverage the multiple energy pathway dependence of triple-negative breast cancer (TNBC) as a therapeutic approach; identify a novel energy metabolism-perturbing therapeutic target; and elucidate the role of endogenous and exogenous mitochondrial perturbation in breast cancer metastasis and progression. 

The excessive energy demand of the highly proliferative TNBC is a crucial driver of metabolic plasticity. I hypothesized that targeting multiple metabolic pathways in a dual-therapy approach in cancer will provide a profound exploitation of metabolic vulnerabilities for efficacious treatment regimens. Thus, I leveraged this energy gluttony to develop a strategy that targets both glycolysis and oxidative phosphorylation, using 2-deoxyglucose (2DG), a hexokinase (HK) inhibitor, and an OXPHOS-targeting gold(III) anticancer agent, respectively.

The in vivo anticancer response demonstrated improved synergy. However, the non-specificity of 2DG in targeting hexokinase led to a specific CRISPR-Cas9-mediated manipulation of HK1, HK2, and HK3 respectively in TNBC cells. Further rigorous target validation studies culminated in the identification of HK3 as a promising therapeutic target in TNBC, revealing it to be a previously uncharacterized and markedly understudied isoform. 

In efforts to glean more insights into cancer energy metabolism and the mitochondrial-modulatory potency of gold(III) complexes, I validated the antitumorigenic, antimetastatic and energy stress-inducing effects of targeting voltage-dependent anion channels 1 (VDAC1), the main regulator of metabolite flux between mitochondria and cytosol, in TNBC using various in vitro and in vivo models. 

Exogenous mitochondria transfer, a term that describes the trafficking of mitochondria from external donors to cancer cells, has gained traction as an emerging concept in cancer energy metabolism. To further our understanding of this concept, I have shown that cancer cells hijack the mitochondria of immune cells, resulting in depletion of metabolic energy available to the immune cells. This study identifies a new therapeutic target and unveils new insight into our understanding of targeting energy metabolism in cancer.

Abstract: The endoplasmic reticulum (ER) chaperone, glucose-regulated protein (GRP78)/binding immunoglobulin protein (BiP)/HSPA5, is a master regulator of Proteostasis, regulating protein folding, the Unfolded Protein Response (UPR) and Endoplasmic Reticulum-associated degradation (ERAD). GRP78 is often overexpressed in many cancers, and this vulnerability has been therapeutically targeted, but therapeutic success has been hampered by resistance and immunosuppression. Despite the availability of a few inhibitors of GRP78, none have achieved clinical approval, highlighting a critical need for new therapeutic strategies. 

Further, the scaffolding functions of GRP78 remain underexplored, and its potential role as a client hub that promotes resistance is not well understood. Targeting ER resident proteins such as GRP78 for degradation remains a significant challenge, as they are largely inaccessible to current targeted degradation approaches. Here, I report the development of peptidomimetic degraders as first-in-class small molecule scaffolds designed to engage the substrate-binding domain of ER chaperone GRP78 and initiate its selective degradation via the endogenous ER-associated degradation (ERAD) pathway. 

Using integrated computational, biochemical, cellular, and multi-omic approaches, my research shows that these peptidomimetic degraders reshape GRP78/BiP conformational dynamics to promote organelle-localized ligase recruitment and proteostatic clearance. Our lead peptidomimetic degrader of GRP78, SGA01 induces ER stress activating the UPR. SGA01 also exhibits favorable metabolic and plasma stability, demonstrates robust pharmacodynamic kinetics with tumor growth suppression in triple-negative breast cancer models, and has no off-target effects. Together, these findings establish a chemical strategy for enforcing ER-restricted protein degradation and provide a tractable framework for targeting chaperone addiction across various malignancies. 

These GRP78 degraders further elucidated the molecular consequences of GRP78 depletion, including disruption of mitochondrial function and ER-mitochondria crosstalk. SGA01-induced degradation of GRP78 causes ER stress, and uncontrolled ER stress amplifies beyond the ER to the mitochondria, leading to disruption of ER mitochondrial crosstalk and mitochondrial dysfunction. SGA01-based probes were designed to map GRP78 protein interactions. In addition to the dipeptide-based peptidomimetic, further development efforts have extended to tripeptides to elucidate the binding rules governing GRP78 degradation. 

In conclusion, we provided a framework for GRP78-targeted degradation using small-molecule peptidomimetics and elucidated the impact of this degradation on other organelles, such as mitochondria, and its relevance in disease models.