2. Academic Validation
  3. OSBP-related protein 3 (ORP3) coupling with VAMP-associated protein A regulates R-Ras activity

OSBP-related protein 3 (ORP3) coupling with VAMP-associated protein A regulates R-Ras activity

  • Exp Cell Res. 2015 Feb 15;331(2):278-91. doi: 10.1016/j.yexcr.2014.10.019.
Marion Weber-Boyvat 1,  Henriikka Kentala 1,  Johanna Lilja 2,  Terhi Vihervaara 1,  Raisa Hanninen 3,  You Zhou 1,  Johan Peränen 4,  Tuula A Nyman 4,  Johanna Ivaska 2,  Vesa M Olkkonen 5
Affiliations

Affiliations

  • 1 Minerva Foundation Institute for Medical Research, Biomedicum 2U, FI-00290 Helsinki, Finland.
  • 2 VTT Medical Biotechnology and Turku Centre for Biotechnology, University of Turku, FI-20520 Turku, Finland.
  • 3 National Institute for Health and Welfare, Biomedicum 1, FI-00290 Helsinki, Finland.
  • 4 Institute of Biotechnology, FI-00014 University of Helsinki, Finland.
  • 5 Minerva Foundation Institute for Medical Research, Biomedicum 2U, FI-00290 Helsinki, Finland; Institute of Biomedicine/Anatomy, FI-00014 University of Helsinki, Finland. Electronic address: vesa.olkkonen@helsinki.fi.
PMID: 25447204 DOI: 10.1016/j.yexcr.2014.10.019
Abstract

ORP3 is an R-Ras interacting oxysterol-binding protein homolog that regulates cell adhesion and is overexpressed in several cancers. We investigated here a novel function of ORP3 dependent on its targeting to both the endoplasmic reticulum (ER) and the plasma membrane (PM). Using biochemical and cell imaging techniques we demonstrate the mechanistic requirements for the subcellular targeting and function of ORP3 in control of R-Ras activity. We show that hyperphosphorylated ORP3 (ORP3-P) selectively interacts with the ER membrane protein VAPA, and ORP3-VAPA complexes are targeted to PM sites via the ORP3 pleckstrin homology (PH) domain. A novel FFAT (two phenylalanines in an acidic tract)-like motif was identified in ORP3; only disruption of both the FFAT-like and canonical FFAT motif abolished the phorbol-12-myristate-13-acetate (PMA) stimulated interaction of ORP3-P with VAPA. Co-expression of ORP3 and VAPA induced R-Ras activation, dependent on the interactions of ORP3 with VAPA and the PM. Consistently, downstream AktS473 phosphorylation and β1-integrin activity were enhanced by ORP3-VAPA. To conclude, phosphorylation of ORP3 controls its association with VAPA. Furthermore, we present evidence that ORP3-VAPA complexes stimulate R-Ras signaling.

Keywords

FFAT motif; Integrin; ORP3; Phosphorylation; R-Ras; VAPA.

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