title: Fendiline inhibits K-Ras plasma membrane localization and blocks K-Ras signal transmission.
abstract: Ras proteins regulate signaling pathways important for cell growth, differentiation, and survival. Oncogenic mutant Ras proteins are commonly expressed in human tumors, with mutations of the K-Ras isoform being most prevalent. To be active, K-Ras must undergo posttranslational processing and associate with the plasma membrane. We therefore devised a high-content screening assay to search for inhibitors of K-Ras plasma membrane association. Using this assay, we identified fendiline, an L-type calcium channel blocker, as a specific inhibitor of K-Ras plasma membrane targeting with no detectable effect on the localization of H- and N-Ras. Other classes of L-type calcium channel blockers did not mislocalize K-Ras, suggesting a mechanism that is unrelated to calcium channel blockade. Fendiline did not inhibit K-Ras posttranslational processing but significantly reduced nanoclustering of K-Ras and redistributed K-Ras from the plasma membrane to the endoplasmic reticulum (ER), Golgi apparatus, endosomes, and cytosol. Fendiline significantly inhibited signaling downstream of constitutively active K-Ras and endogenous K-Ras signaling in cells transformed by oncogenic H-Ras. Consistent with these effects, fendiline blocked the proliferation of pancreatic, colon, lung, and endometrial cancer cell lines expressing oncogenic mutant K-Ras. Taken together, these results suggest that inhibitors of K-Ras plasma membrane localization may have utility as novel K-Ras-specific anticancer therapeutics.
authors.affiliation: Department of Integrative Biology and Pharmacology, The University of Texas Medical School at Houston, Houston, Texas, USA.
authors.forename: Dharini
authors.initials: D
authors.lastname: van der Hoeven
authors.forename: Kwang-jin
authors.initials: KJ
authors.lastname: Cho
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Ma
authors.forename: Sravanthi
authors.initials: S
authors.lastname: Chigurupati
authors.forename: Robert G
authors.initials: RG
authors.lastname: Parton
authors.forename: John F
authors.initials: JF
authors.lastname: Hancock
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002460:Cell Line; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D005275:Fendiline / Q000494:pharmacology*; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D061985:Madin Darby Canine Kidney Cells; D008745:Methylation; D008856:Microscopy, Fluorescence; D009154:Mutation; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras); D015398:Signal Transduction / Q000187:drug effects*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D002121:Calcium Channel Blockers; C117307:KRAS protein, human; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins; D005275:Fendiline