398.2 - A phosphoinositide cascade regulates a receptor recycling pathway

Lois Weisman (University of Michigan), Sai Srinivas Panapakkam Giridharan (University of Michigan, University of Michigan), Guangming Luo (University of Michigan, University of Michigan), Pilar Rivero-Rios (University of Michigan, University of Michigan), Noah Steinfeld (University of Michigan, University of Michigan), Helene Tronchere (INSERM U1048 I2MC, Université Paul Sabatier), Amika Singla (University of Texas Southwestern Medical Center, University of Texas Southwestern Medical Center), Ezra Burstein (University of Texas Southwestern Medical Center, University of Texas Southwestern Medical Center), Daniel Billadeau (Mayo Clinic, Mayo Clinic), Michael Sutton (University of Michigan, University of Michigan, University of Michigan)

Phosphatidylinositol polyphosphates (PIPs) are essential cellular regulators. Each PIP transiently appears at specific membranes to regulate the spatial and temporal recruitment of unique downstream effectors. Importantly, most PIPs serve as both signaling lipids, and as precursors for other PIPs. These precursor-product relationships likely form cascades of pathways, which would provide a way for PIPs to coordinate events both spatially and temporally. Here we uncover a pathway on endosomes, which is likely governed by a cascade of three phosphoinositide lipids. The pathway is specific for the recycling of some receptors to the plasma membrane and is mediated by sorting-nexin SNX17, and the Retriever, WASH and CCC complexes. We discover that PIKfyve and an upstream PI3-kinase, VPS34 positively regulates this pathway. VPS34 produces PI3P, which provides the substrate for PIKfyve to generate PI3,5P2, which is then further converted to PI5P by myotubularin 3-phosphatases.  We show that PIKfyve regulates recycling of cargoes including integrins, receptors that control cell migration. Furthermore, endogenous PIKfyve colocalizes with SNX17, Retriever, WASH and CCC complexes on endosomes. Importantly, PIKfyve inhibition causes a loss of Retriever and CCC from endosomes. In addition, we show that recruitment of SNX17 is an early step and requires VPS34. These discoveries suggest that VPS34 and PIKfyve coordinate an ordered pathway to regulate recycling from endosomes and suggest how PIKfyve functions in cell migration. More broadly, these findings provide more general insights into mechanisms for how cells regulate the levels of some receptors at the cell surface.

Support or Funding Information

Supported by R01-NS099340 and R01 NS064015 to LSW, R01-DK107733 to EB and DDB, and by the University of Michigan Protein Folding Diseases Fast Forward Initiative. SSPG was supported in part by a postdoctoral fellowship from the American Heart Association, 14POST20480137. GL was supported in part by a postdoctoral fellowship from the American Heart Association, 19POST34450253.

lt;pgt;Supported by R01-NS099340 and R01 NS064015 to LSW, R01-DK107733 to EB and DDB, and by the University of Michigan Protein Folding Diseases Fast Forward Initiative. SSPG was supported in part by a postdoctoral fellowship from the American Heart Association, 14POST20480137. GL was supported in part by a postdoctoral fellowship from the American Heart Association, 19POST34450253.lt;/pgt;