INSULIN INDUCES THE EXOCYTIC TRAFFIC OF LRP1 FROM GSV?LIKE STRUCTURAL VESICLES

VAZQUEZ MM; BARCELONA PF; CHIABRANDO GA; ACTIS DATO VIRGINIA; SANCHEZ MC

Congreso; 52th Annual Meeting Argentine Society for Biochemistry and Molecular Biology LII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2016

Glucose transporter type 4 (GLUT4) is an insulin-regulated glucose transporter only expressed in adipose and muscle cells. In these cells GLUT4 is stored in specialized structural vesicles termed GSV. LDL receptor-related protein 1 (LRP1) is also detected in GSV.However, LRP1 is expressed in other cells that not contain GLUT4, such as Muller Glial cells (MGCs). This receptor is intracellularly stored in non well-characterized structural vesicles from which can be sorted to plasma membrane (PM) in the presence of the alpha2-Macroglobulin (a LRP1-related ligand) or insulin (a LRP1-nonrelated ligand) through a putative exocytic route. We hypothesize that LRP1 is stored in GSV-like structural vesicles in all types of cells. Herein, we characterize the structural vesicles storing LRP1 in a MGC line, MIO-M1. By biotin-labeling protein assay we demonstrated that LRP1 translocate to PM after insulin stimulation (100 nM; 30 min), which was inhibited by the expression of a negative mutant of Rab10 GTPase. By confocal microscopy we found the LRP1 colocalization with mCherry-GLUT4-Myc and sortilin, a marker of GSV. Finally, we demonstrate that HA-mLRP4-GFP and mCherry-GLUT4-Myc were trafficked to PM in insulin-stimulated cells. Thus, we conclude that LRP1 is stored in structural vesicles with GSV properties in MIO-M1 cells, from which is trafficked to PM through an exocytic pathway.