The Witze Laboratory is interested in studying the mechanisms by which extracellular signaling controls polarized cell behavior and how alterations in these processes contribute to tumor initiation, metastasis, and drug sensitivity.
Determining the mechanism controlling cell polarity is critical to our understanding of both homeostatic and disease states including generation of cell heterogeneity through asymmetric cell divisions and efficient cell migration during cancer metastasis. Although genetic and developmental model systems have identified many of the players that regulate cell polarity the mechanisms that regulate cell polarity are still poorly understood. One signaling pathway that regulates cell polarity during embryonic development is the noncanonical Wnt5a signaling pathway. Unlike the canonical Wnt/beta-catenin dependent pathway the noncanonical Wnt5a pathway is still poorly defined in part due to markers for signal activation. We have recently discovered that Wnt5a signaling induces depalmitoylation of cell adhesion molecules CD44 and MCAM. Palmitoylation is the addition of the fatty acid palmitate to cysteine residues, which mediates the localization and activity of a variety of proteins including Ras, thereby serving as a novel modification that has the ability to alter signaling pathways in cancer. Mutating the palmitoylated cysteine prevents palmitoylation, promotes asymmetric localization of MCAM, and increases cell invasion in vitro and in vivo. This is a novel function for both Wnt5a and protein palmitoylation. We are currently focusing on the mechanism of Wnt5a induced depalmitoylation and the function of the family of protein palmitoyl transferases called DHHC proteins in cancer progression.
A second focus of the lab is the regulation of receptor tyrosine kinase signaling in cancer. The epidermal growth factor receptor (EGFR) is involved in both cancer initiation and progression. Silencing DHHC20 elevates EGFR expression and amplifies EGFR activation and downstream signaling in response to EGF in basal breast cancer and lung cancer cells. Our findings demonstrate that DHHC20 palmitoylates EGFR on its C-terminal tail and suppresses EGFR signaling. Site specific mutation of palmitoylated C-terminal cysteine residues causes EGFR activation independent of EGF. We have shown that the increased EGFR activation caused by DHHC20 shRNA increases sensitivity of breast and lung cancer cells to the EGFR inhibitor Gefitinib. Our findings identify palmitoylation as a novel modification of EGFR that regulates receptor activation. We are currently determining the function of EGFR palmitoylation in vivo and are investigating the role of palmitoylation on the regulation of other receptor tyrosine kinases.
The Witze lab is accepting applications for postdoctoral positions. Please email your CV to email@example.com.
01. Bloss TA, Witze ES, Rothman JH. Suppression of CED-3-independent apoptosis by mitochondrial betaNAC in Caenorhabditis elegans. Nature. 424(6952):1066-71. 2003.
02. Witze ES, Old WM, Resing KA, Ahn NG. Mapping protein post-translational modifications with mass spectrometry. Nat Methods. 4(10):798-806. 2007.
03. Witze ES, Litman ES, Argast GM, Moon RT, Ahn NG. Wnt5a control of cell polarity and directional movement by polarized redistribution of adhesion receptors. Science. 320(5874):365-9. 2008.
04. Witze ES, Field ED, Hunt DF, Rothman JH. C. elegans pur alpha, an activator of end-1, synergizes with the Wnt pathway to specify endoderm. Dev Biol. 327(1):12-23. 2009.
05. Old WM, Shabb JB, Houel S, Wang H, Couts KL, Yen CY, Litman ES, Croy CH, Meyer-Arendt K, Miranda JG, Brown RA, Witze ES, Schweppe RE, Resing KA, Ahn NG. Functional proteomics identifies targets of phosphorylation by B-Raf signaling in melanoma. Mol Cell. 34(1):115-31. 2009.
06. Kabuyama Y, Litman ES, Templeton PD, Metzner SI, Witze ES, Argast GM, Langer SJ, Polvinen K, Shellman Y, Chan D, Shabb JB, Fitzpatrick JE, Resing KA, Sousa MC, Ahn NG. A mediator of Rho-dependent invasion moonlights as a methionine salvage enzyme. Mol Cell Proteomics. 8(10):2308-20. 2009.
07. Sayers CM, Papandreou I, Guttmann DM, Maas NL, Diehl JA, Witze ES, Koong AC, Koumenis C. Identification and Characterization of a Potent Activator of P53-Independent Cellular Senescence Via a Small Molecule Screen for Modifiers of the Integrated Stress Response. Mol Pharmacol. 83(3):594-604. 2013.
08. Witze ES, Connacher MK, Houel S, Schwartz MP, Morphew MK, Reid L, Sacks DB, Anseth KS, Ahn NG. Wnt5a directs polarized calcium gradients by recruiting cortical endoplasmic reticulum to the cell trailing edge. Dev Cell. 26(6):645-57. 2013.
09. Londoño Gentile T, Lu C, Lodato PM, Tse S, Olejniczak SH, Witze ES, Thompson CB, Wellen KE DNMT1 is regulated by ATP-citrate lyase and maintains methylation patterns during adipocyte differentiation. Mol Cell Biol. 33(19):3864-78. 2013.
10. Wang W, Terkowski S, Ekaireb R, Runkle K, Putzke A, Witze E Wnt5a induced protein depalmitoylation regulates developmental cell movement and tumor cell invasion. Oncogenesis (4) 2015.
11. Wang W, Snyder N, Worth AJ, Blair IA, Witze ES Regulation of lipid synthesis by the RNA helicase Mov10 controls Wnt5a production. JBC 290(25): 15707-16. 2015.
12. Runkle K, Kharbanda A, Stypulkowski E, Cao X-J, Wang W, Garcia, B, Witze E Inhibition of DHHC20 mediated EGFR palmitoylation creates a dependence on EGFR signaling. Molecular Cell 62(3):385–396, 2016 .
Akriti Kharbanda - Graduate Student
Ewa Stypulkowski - Graduate Student
Katelyn Carlin - Administrative Coordinator
Rochelle Sadeghi - Graduate Student
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