INSULIN REGULATES THE LRP1 TRANSLOCATION TO THE CELL SURFACE IN MÜLLER GLIAL CELLS

ACTIS DATO V; VAZQUEZ MM; GUTIERREZ V; BARCELONA PF; BONACCI GR; SÁNCHEZ MC; FADER CM; CHIABRANDO GA

Paraná,Entre ríos

Congreso; LIV Reunión Anual Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2018

SAIB

Low-density lipoprotein (LDL) receptor-related protein-1 (LRP1) is an endocytic and signaling receptor expressed in retinal Müller glial cells (MGCs). This receptor regulates the molecular activity of different membrane proteins, included insulin receptor (IR), which is involved with the MGC motility and metabolism. Moreover, insulin increases the LRP1 expression in the cell surface of neurons and hepatic cells, although the intracellular route of this LRP1 sorting in these cells and MGCs is not well established. Hence, in the present work we investigate the insulin induced LRP1 translocation to the plasma membrane in human retinal MGC-derived cell line, MIO-M1. By electron microscopy we observed that LRP1 is stored in small vesicles (mean diameter range of 100?120 nm), which were positive for sortilin and VAMP2, and also incorporated GLUT4 when it was transiently transfected. Next, by biotin-labeling protein assay we observed that the LRP1 translocation to the plasma membrane was promoted by insulin-regulated exocytosis through intracellular activation of the IR/PI3K/Akt axis and Rab-GTPase proteins, such as Rab8A and Rab10. Moreover, these Rab-GTPases regulated both the constitutive and insulin-induced LRP1 translocation to the plasma membrane. Finally, we found that dominant-negative Rab8A and Rab10 mutants impaired insulin-induced intracellular signaling of the IR/PI3K/Akt axis, suggesting that these GTPase proteins as well as LRP1 cell surface level are involved in insulin-induced IR activation. We propose that insulin-induced LRP1 translocation to the plasma membrane is essential for IR activity, which might be relevant for the function ofMGCs during pathological disorders of the retina associated with insulin resistance.