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Mark PhilipsProfessor, Department of Medicine
Professor, Department of Cell Biology
Professor, Department of Biochemistry and Molecular Pharmacology
Director for Basic Research CI
Assoc Director for Basic Research CI
522 First Avenue
New York, NY 10016
Education1982 — Columbia College of Physicians and Surgeons, Medical Education
— He was a Fellow in the Division of Rheumatology, 1985-1986, and Chief Fellow, Division of Rheumatology, 1986-1988 at NYU Medical Center, Clinical Fellowships
1982-1985 — Dr. Philips completed his Residency in Medicine at Bellevue Hospital, New York University (NYU) Medical Center, Residency Training
Research SummaryOur laboratory is primarily interested in the cell biology of GTPases. GTPases are ubiquitous elements of signaling pathways, including those regulating cell growth and differentiation. Virtually all cellular processes utilize GTPases as regulatory elements including processes that control the immune response. Thus, although our work has immediate relevance to cancer, insights from our studies may be relevant to a wide variety of human diseases including inflammatory and autoimmune disorders.
The protooncogene ras and closely related GTPases are among a class of proteins that are synthesized as soluble molecules in the cytosol and are then targeted to membranes by a series of posttranslational modifications of a C-terminal CAAX sequence that includes prenylation, proteolysis, and carboxyl methylation. Of these modifications, only carboxyl methylation is reversible and may therefore have a signaling function. We therefore focused on the enzyme that catalyzes this modification, prenylcysteine carboxyl methyltransferase, and recently cloned its gene.
Prenylcysteine carboxyl methyltransferase proved to be a multiple membrane spanning protein that is expressed in ER and Golgi but not plasma membrane (see figure). This observation was surprising since it implied that ras, synthesized in the cytosol and destined for the plasma membrane, must make a detour to the ER to complete processing. The ER processing of ras led us to hypothesize that ras is transported to plasma membrane via the vesicular transport system. Using green fluorescent protein-tagged ras proteins we showed that this model is correct. We also showed that carboxyl methylation is required for vesicular transport of ras. We hope to exploit this previously unappreciated aspect of ras biology to develop novel anticancer therapies.
In more recent work we have tested the hypothesis that intracellular ras can be activated and regulate signaling pathways and proved it correct. We accomplished this by developing a novel fluorescent probe that reports when and where Ras becomes activated in living cells. We consider our probe for activated ras a prototyped of a class of molecules that can serve as fluorescent reporters of signaling events in living cells and thereby elucidate many previously inaccessible aspects of signal transduction.
Research InterestsProcessing and membrane targeting of GTPases.
VPS35 binds farnesylated N-Ras in the cytosol to regulate N-Ras trafficking
Zhou, Mo; Wiener, Heidi; Su, Wenjuan; Zhou, Yong; Liot, Caroline; Ahearn, Ian; Hancock, John F; Philips, Mark R. VPS35 binds farnesylated N-Ras in the cytosol to regulate N-Ras trafficking. Journal of cell biology. 2016 Aug 8;214(4):445-458 (2213572)
Targeting RAS Membrane Association: Back to the Future for Anti-RAS Drug Discovery?
Cox, Adrienne D; Der, Channing J; Philips, Mark R. Targeting RAS Membrane Association: Back to the Future for Anti-RAS Drug Discovery? [Editorial]. Clinical cancer research. 2015 Apr 15;21(8):1819-1827 (1532252)
p27kip1 controls H-Ras/MAPK activation and cell cycle entry via modulation of MT stability
Fabris, Linda; Berton, Stefania; Pellizzari, Ilenia; Segatto, Ilenia; D'Andrea, Sara; Armenia, Joshua; Bomben, Riccardo; Schiappacassi, Monica; Gattei, Valter; Philips, Mark R; Vecchione, Andrea; Belletti, Barbara; Baldassarre, Gustavo. p27kip1 controls H-Ras/MAPK activation and cell cycle entry via modulation of MT stability. Proceedings of the National Academy of Sciences of the United States of America (PNAS). 2015 Oct 28;112(45):13916-13921 (1817572)
The differential palmitoylation States of N-ras and h-ras determine their distinct Golgi subcompartment localizations
Lynch, Stephen J; Snitkin, Harriet; Gumper, Iwona; Philips, Mark R; Sabatini, David; Pellicer, Angel. The differential palmitoylation States of N-ras and h-ras determine their distinct Golgi subcompartment localizations. Journal of cellular physiology. 2015 Mar ;230(3):610-619 (1360222)
Seeing is believing: Ras dimers observed in live cells
Philips, Mark R; Der, Channing J. Seeing is believing: Ras dimers observed in live cells. Proceedings of the National Academy of Sciences of the United States of America (PNAS). 2015 Jul 30;112(32):9793-9794 (1698672)