Intracellular traffic of LRP1 and GLUT4 in alpha2-macroglobulin-stimulated cells.

ACTIS DATO VIRGINIA; JALDIN FINCATI J; SANCHEZ MC; CHIABRANDO GA,

Otro; L Reunion anual de la SAIB; 2014

Low density lipoprotein receptor-related protein 1 (LRP1) is an endocytic and signaling receptor, which binds alpha 2-macroglobulin-protease complex (a2M*) and promotes cell migration of Muller glial-derived cell line, MIO-M1. The a2M* induces LRP1 translocation to plasma membrane (PM) by two posible pathways; i) Rab4 and Rab11-dependent recycling, and ii) exocytosis from LRP1-stored vesicles and Rab11-independent pathway, which can be also stimulated by insulin. Glucose transporter type 4 (GLUT4) is a insulin-regulated glucose transporter found in adipose and muscle tissues. Specialized GLUT4 storage vesicles (GSV) can be translocated to PM by insulin through a Rab10-dependent pathway, increasing the glucose uptake. The failure of GLUT4 translocation is involved in insulin resistance and type 2 diabetes mellitus. LRP1 is the main protein component of GSV, although its function is not completely understood. To examine whether a2M* induces GSV translocation to PM, we have characterized the subcellular localization of LRP1 and GLUT4 in MIO-M1 cells. By confocal microscopy and biotin-labeling protein assay we determine that LRP1 and GLUT4 shown a high colocalization in intracellular vesicles, compatible with GSV, and LRP1 was translocated to PM by a2M*, which was unaffected by the presence of a dominant-negative Rab11 mutant. We conclude that a2M* induced LRP1 traffic to PM from GSV.