Exogenous lysophospholipids with large head groups perturb clathrin‐mediated endocytosis

• Published in: Traffic (Copenhagen, Denmark) Vol. 18; no. 3; pp. 176 - 191
• Main Authors: Ailte, Ieva, Lingelem, Anne Berit D., Kvalvaag, Audun S., Kavaliauskiene, Simona, Brech, Andreas, Koster, Gerbrand, Dommersnes, Paul G., Bergan, Jonas, Skotland, Tore, Sandvig, Kirsten
• Format: Journal Article
• Language: English
• Published: Former Munksgaard John Wiley & Sons A/S 01.03.2017; Wiley Subscription Services, Inc
• Subjects: actin; Actins - metabolism; AP2; Cell Line, Tumor; Cell Membrane - metabolism; Cell Membrane - physiology; clathrin; Clathrin - metabolism; Coated Pits, Cell-Membrane - metabolism; Endocytosis; Endocytosis - physiology; HeLa Cells; Humans; lysophosphatidylinositol; lysophospholipids; Lysophospholipids - metabolism; plasma membrane; transferrin; Transferrin - metabolism; actin; AP2; clathrin; lysophospholipids; plasma membrane; transferrin; endocytosis; lysophosphatidylinositol
• ISSN: 1398-9219; 1600-0854
• DOI: 10.1111/tra.12468

In this study, we have investigated how clathrin‐dependent endocytosis is affected by exogenously added lysophospholipids (LPLs). Addition of LPLs with large head groups strongly inhibits transferrin (Tf) endocytosis in various cell lines, while LPLs with small head groups do not. Electron and total internal reflection fluorescence microscopy (EM and TIRF) reveal that treatment with lysophosphatidylinositol (LPI) with the fatty acyl group C18:0 leads to reduced numbers of invaginated clathrin‐coated pits (CCPs) at the plasma membrane, fewer endocytic events per membrane area and increased lifetime of CCPs. Also, endocytosis of Tf becomes dependent on actin upon LPI treatment. Thus, our results demonstrate that one can regulate the kinetics and properties of clathrin‐dependent endocytosis by addition of LPLs in a head group size‐ and fatty acyl‐dependent manner. Furthermore, studies performed with optical tweezers show that less force is required to pull membrane tubules outwards from the plasma membrane when LPI is added to the cells. The results are in agreement with the notion that insertion of LPLs with large head groups creates a positive membrane curvature which might have a negative impact on events that require plasma membrane invagination, while it may facilitate membrane bending toward the cell exterior. Exogenous addition of saturated lysophospholipids with large head groups to cells strongly inhibits clathrin‐mediated endocytosis of transferrin: the number of endocytic pits decreases, the lifetime of AP2‐positive pits increases and actin dependency is induced. Experiments with optical tweezers show that less force is required to pull membrane tubules outwards, suggesting that insertion of lysophospholipids in the outer leaflet bends the membrane outwards and counteracts formation of invaginations.