AGGREGATED LDL AFFECTS THE REGULATORY ACTION OF LRP1 ON THE INSULIN-DEPENDENT INTRACELLULAR SIGNALING AND GLUT4 TRAFFICKING IN HL-1 CARDIOMYOCYTES

ACTIS DATO V; BENITEZ AMARO A; NASARRE R; GUTIERREZ V; VAZQUEZ MM; LLORENTE CORTES V; CHIABRANDO GA

Ciudad Autónoma de Buenos Aires

Congreso; Reunion conjunta de Sociedades de Biociencias; 2017

SAIB en conjunto con 10 sociedades científicas en biociencias del país.

Diabetes mellitus (DM) is a metabolic disorder mainly characterizedby hyperglycemia, dyslipidemia and hyperinsulinemia, andcardiovascular disease (CVD) is the main complication of DM. DMpatients usually have increased levels of atherogenic subfractionsof low-density lipoproteins (LDL), such as aggregated LDL (agLDL).This latter lipoprotein is responsible to induce anomalous intracellularlipid accumulation in cardiomyocytes in a low-density lipoproteinreceptor-related protein-1 (LRP1)-dependent manner. LRP1 is anendocytic and signaling receptor, belonging to the LDL receptor family.Moreover, LRP1 regulates the intracellular trafficking of membraneproteins and vesicles, including insulin receptor (IR), GLUT4and GSVs (GLUT4 storage vesicles). Thus, it has been suggestedthat a functional deficiency of LRP1 would be directly associatedwith insulin resistance disorders. In the present work, we evaluatewhether agLDL via its interaction with LRP1 may affect the insulin-induced intracellular signaling and GLUT4 trafficking to the plasmamembrane (PM) in HL-1 cardiomyocytes. By quantitative PCRand Western blot analysis we determined that LRP1 and GLUT4expression were unaffected after agLDL treatment for 8 h at 37 °C.By confocal microscopy we found a substantial modification of theintracellular localization of LRP1 and GLUT4 in agLDL-stimulatedcells. Also, after insulin stimulus (100 nM) in agLDL-preincubatedcells, a decreased level of Akt and AS160 phosphorylation was observedcompared to unpreincubated cells. By immunoprecipitationwe found that agLDL-preincubated cells showed a weakly molecularassociation between IR and LRP1 with respect to control conditions.Finally, by biotin-labeling protein assay we demonstrated that agLDLreduced the GLUT4 translocation to the plasma membrane in insulin-stimulated cells. Thus, we conclude that LRP1 is a key regulatorof insulin response and glucose metabolism in cardiomyocytes, beingits action affected by agLDL.