ENDOCYTIC RECYCLING OF LRP1 IN ALPHA 2- MACROGLOBULIN-STIMULATED CELLS

JALDIN-FINCATI JR; BARCELONA PF; SÁNCHEZ MC; CHIABRANDO GA

Mendoza

Congreso; XLVIII Reunion Anual SAIB; 2012

SAIB

The LDL receptor-related protein 1 (LRP1) is an endocytic and signaling receptor, which play an key role in the cellular migration and proliferation. Previously we demonstrated that alpha 2-Macroglubulin (a2M*) induced intracellular signaling activation via LRP1, which is characterized by PKC and MAPK activation. Our hypothesis is that the cellular function of LRP1 involves the endocytic recycling and cell surface sorting of this receptor in a2M*-stimulated cells. Hence, in this work we tried to characterize the endocytic recycling and cell membrane sorting of LRP1 in MIO-M1 and HeLa cells stimulated with a2M*. Using confocal microscopy, flow cytometry and a recombinant mini-receptor version of LRP1 (mLRP4-GFP) we demonstrated that a2M* induced the increase of LRP1 localization in Rab5 and Rab11-recycling compartments respect to cells without stimulation. Then, LRP1 immunoprecipitation techniques of biotin-labeled cell surface proteins were used to show that a2M* promoted the intracellular sorting of the constitutive LRP1 and mLRP4 to the cell membrane. This sorting was partially blocked by the negative dominant mutant form of Rab11. However, other Rab forms, probably Rab8 and Rab6, could be involved in this sorting process. Our data suggest that the LRP1 function in a2M*-stimulated cells is dependent on the endocytic recycling of this receptor.