The small GTPase KRAS, which is frequently mutated in human cancers, must be localized to the plasma membrane (PM) for biological activity. We recently showed that the KRAS C-terminal membrane anchor exhibits exquisite lipid-binding specificity for select species of phosphatidylserine (PtdSer). We therefore investigated whether reducing PM PtdSer content is sufficient to abrogate KRAS oncogenesis. Oxysterol-related binding proteins ORP5 and ORP8 exchange PtdSer synthesized in the ER for phosphatidylinositol-4-phosphate (PI4P) synthesized in the PM. We show that depletion of ORP5 or ORP8 reduced PM PtdSer levels, resulting in extensive mislocalization of KRAS from the PM. Concordantly, ORP5 or ORP8 depletion significantly reduced proliferation and anchorage-independent growth of multiple KRAS-dependent cancer cell lines, and attenuated KRAS signaling in vivo. Similarly, functionally inhibiting ORP5 and ORP8 by inhibiting PI4KIIIα-mediated synthesis of PI4P at the PM selectively inhibited the growth of KRAS-dependent cancer cells over normal cells in vitro and in vivo. Hence, inhibiting KRAS function through regulating PM PtdSer content may represent a viable strategy for KRAS-driven cancers.
","abstract_html":"<p>The small GTPase KRAS, which is frequently mutated in human cancers, must be localized to the plasma membrane (PM) for biological activity. We recently showed that the KRAS C-terminal membrane anchor exhibits exquisite lipid-binding specificity for select species of phosphatidylserine (PtdSer). We therefore investigated whether reducing PM PtdSer content is sufficient to abrogate KRAS oncogenesis. Oxysterol-related binding proteins ORP5 and ORP8 exchange PtdSer synthesized in the ER for phosphatidylinositol-4-phosphate (PI4P) synthesized in the PM. We show that depletion of ORP5 or ORP8 reduced PM PtdSer levels, resulting in extensive mislocalization of KRAS from the PM. Concordantly, ORP5 or ORP8 depletion significantly reduced proliferation and anchorage-independent growth of multiple KRAS-dependent cancer cell lines, and attenuated KRAS signaling <em>in vivo</em>. Similarly, functionally inhibiting ORP5 and ORP8 by inhibiting PI4KIIIα-mediated synthesis of PI4P at the PM selectively inhibited the growth of KRAS-dependent cancer cells over normal cells <em>in vitro</em> and <em>in vivo</em>. Hence, inhibiting KRAS function through regulating PM PtdSer content may represent a viable strategy for KRAS-driven cancers.</p>","abstract_has_math":false,"creators":["Kattan, Walaa E","0000-0002-0599-9744
"],"institution":null,"degree_name":"Doctor of Philosophy (PhD)","degree_level":"Dissertation (PhD)","degree_discipline":null,"degree_department":null,"school":null,"contributors":["John F. Hancock","Jeffrey Frost","E. Scott Kopetz"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2021,"date_issued":"2021-08-01T07:00:00Z","date_published":"2021-08-01T07:00:00Z","updated_at":"2026-07-24T05:49:16Z","subjects":["KRAS","PI4KA","ORP5","ORP8","phosphatidylserine","PI4P","cancer","drug repurposing","Animal Experimentation and Research","Cancer Biology","Cell Biology","Enzymes and Coenzymes","Lipids","Molecular Genetics"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://digitalcommons.library.tmc.edu/utgsbs_dissertations/1120","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["John F. Hancock","Jeffrey Frost","E. Scott Kopetz"]},{"key":"dc:creator","label":"Author","values":["Kattan, Walaa E","0000-0002-0599-9744
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"]},{"key":"dc:title","label":"Title","values":["Targeting Plasma Membrane Phosphatidylserine Content to Inhibit Oncogenic Kras Function"]}]}],"canonical_facts":{"dc:contributor":["John F. Hancock","Jeffrey Frost","E. Scott Kopetz"],"dc:creator":["Kattan, Walaa E","0000-0002-0599-9744
"],"dc:date.available":["2022-07-29T07:00:00Z"],"dc:description.abstract":["The small GTPase KRAS, which is frequently mutated in human cancers, must be localized to the plasma membrane (PM) for biological activity. We recently showed that the KRAS C-terminal membrane anchor exhibits exquisite lipid-binding specificity for select species of phosphatidylserine (PtdSer). We therefore investigated whether reducing PM PtdSer content is sufficient to abrogate KRAS oncogenesis. Oxysterol-related binding proteins ORP5 and ORP8 exchange PtdSer synthesized in the ER for phosphatidylinositol-4-phosphate (PI4P) synthesized in the PM. We show that depletion of ORP5 or ORP8 reduced PM PtdSer levels, resulting in extensive mislocalization of KRAS from the PM. Concordantly, ORP5 or ORP8 depletion significantly reduced proliferation and anchorage-independent growth of multiple KRAS-dependent cancer cell lines, and attenuated KRAS signaling in vivo. Similarly, functionally inhibiting ORP5 and ORP8 by inhibiting PI4KIIIα-mediated synthesis of PI4P at the PM selectively inhibited the growth of KRAS-dependent cancer cells over normal cells in vitro and in vivo. Hence, inhibiting KRAS function through regulating PM PtdSer content may represent a viable strategy for KRAS-driven cancers.
"],"dc:identifier":["https://digitalcommons.library.tmc.edu/utgsbs_dissertations/1120"],"dc:subject":["KRAS","PI4KA","ORP5","ORP8","phosphatidylserine","PI4P","cancer","drug repurposing","Animal Experimentation and Research","Cancer Biology","Cell Biology","Enzymes and Coenzymes","Lipids","Molecular Genetics"],"dc:title":["Targeting Plasma Membrane Phosphatidylserine Content to Inhibit Oncogenic Kras Function"],"thesis:degree_level":["Dissertation (PhD)"],"thesis:degree_name":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-24T05:49:16Z"}