Florin Saitis, “Reconstituting Full-Length Mitochondrial Fission Protein 1, Fis1, and Assessing Its Inhibitory Role in Pancreatic Cancer”
Mentor: Blake Hill, MCW Cancer Center
Poster #83

Mitochondrial fission is the process by which mitochondria divide and is necessary for organelle segregation into daughter cells during cytokinesis. Excessive mitochondrial fission has been linked to increased tumor growth in many cancers, including pancreatic cancer. Pancreatic cancer is one of the deadliest cancers in the U.S., with a 5-year survival rate of 10%. The goal of this project is to advance a novel therapeutic route against pancreatic cancer by targeting mitochondrial fission proteins. Inhibition of mitochondrial fission, either genetically or pharmacologically, blocks oncogenesis. Dynamin-related protein 1 (Drp1) performs mitochondrial fission and is recruited to sites of fission by mitochondrial fission protein 1 (Fis1). By inhibiting Fis1, which is three times more upregulated in pancreatic cancer than Drp1, mitochondrial fission is restricted. We have developed pep213, a novel peptide inhibitor, that inhibits Fis1 and prevents mitochondrial fission. However, pep213 was designed to block a version of Fis1 that lacks its transmembrane domain that anchors it to the outer mitochondrial membrane (Fis1ΔTM), and it has not been tested in vitro against Full-length Fis1. We hypothesize that inhibitors designed against Fis1ΔTM will have an enhanced affinity for membrane-anchored Fis1. To this goal, Full-length Fis1 was successfully reconstituted in a detergent micelle. Using microscale thermophoresis, it was determined that Full-length Fis1 binds with Drp1 at a similar binding affinity as Fis1ΔTM. The Fis1 cytoplasmic domain is destabilized in the presence of detergent micelles and appears to adopt more than one single conformation. Nuclear magnetic resonance (NMR) also revealed chemical shift perturbations of residues in the Full-length Fis1 regulatory arm region compared to Fis1ΔTM. We then tested how inhibited Fis1 impacts pancreatic cancer cell proliferation by using cellular proliferation assays and discovered that pharmacologic inhibition of Fis1 by pep213, and not a control peptide, in mouse pancreatic cancer cells reduced cell proliferation by 75%.