Title: Elucidating protein-protein interactions for GDAP1 and GDAP1L1
Abstract:
The mitochondria require the coordination of numerous proteins to function in nuanced ways to maintain cellular homeostasis. One protein implicated in mitochondrial dynamics is ganglioside-induced differentiation-associated protein 1 (GDAP1). GDAP1 is located on the outer mitochondrial membrane (OMM) and is currently classified in a larger protein family known as glutathione-S-transferases (GST). However, efforts in identifying a GST-associated ligand or enzymatic activity have been largely unsuccessful. Interestingly, GDAP1 single point mutations are associated with an inherited peripheral neuropathy known as Charcot-Marie-Tooth disease (CMT). CMT patient data provides a unique opportunity to inform function hypotheses. Indeed, GDAP1 CMT mutants are not clustered in the canonical binding pocket as one might expect if its function involves typical enzymatic activity. Rather, the CMT hotspot is at the canonical dimerization interface, which would indicate a protein-protein interaction (PPI) that is disrupted in CMT patients.
In parallel with GDAP1 research, we also have the possibility to elucidate the function of the closest paralog of GDAP1, ganglioside-induced differentiation-associated protein 1-like 1 (GDAP1L1). Given its sequence and domain similarities to GDAP1, GDAP1L1 is hypothesized to have a similar function, potentially with respect to the mitochondria. Overall, the structure and biochemical role of GDAP1 and GDAP1L1 are unknown and determining a PPI would shed light on broader mitochondrial regulation and disease.
Title: Investigating the Role of UBL7 in the Ubiquitin-Proteasome Pathway in Ovarian Cancer Cells
Abstract:
Ovarian cancer is one of the deadliest cancers affecting women, is highly resistant to chemotherapeutics, and has a high rate of recurrence. One underexplored aspect of chemotherapy resistance and recurrence is quiescence, where cells distal from a nutrient source exit the cell cycle, remain non-proliferative, but maintain low metabolic activity. Single cell sequencing of quiescent cells showed genes differentially expressed between quiescent and proliferating cells, including numerous genes associated with the ubiquitin-proteasome pathway. One such gene, UBL7, is more highly expressed in quiescent cells and—based on the presence of a ubiquitin-association domain (UBA) and a ubiquitin-binding domain (UBL)—is predicted to help recruit ubiquitinated proteins to the proteasome for degradation. Our goal is to identify UBL7 substrate(s) to understand its role in ovarian cancer quiescence. Initial results show siRNA knockdown of UBL7 does not increase poly-ubiquitination in HEK293 and ovarian cancer cells, indicating UBL7 does not target all ubiquitinated proteins and may have specific substrates. Additionally, there is no significant change in LC3B, a marker of autophagy. A BLAST search revealed homology between three regions in UBL7 and a ubiquilin, which plays important roles in protein quality control. Future experiments will include immunoprecipitation and mass spectrometry to identify UBL7 binding partners. The design of a CRISPR UBL7 knockout ovarian cancer cell line and experiments examining sensitivity to cancer therapeutics will provide insights into UBL7's role in chemotherapy resistance and quiescence.
VanDemark and Brodsky Lab
Friday, September 13th, 2024
12:00PM
Langley A219B