CB-C07.
ENDOCYTIC RECYCLING OF LRP1 IN ALPHA 2-
MACROGLOBULIN-STIMULATED CELLS
Jaldin Fincati JR, Barcelona PF, Sánchez MC, Chiabrando GA.
CIBICI (CONICET) Departamento de Bioquímica Clínica
Facultad de Ciencias Químicas Univ Nac Córdoba. E-mail:
jfincati@bioclin.fcq.unc.edu.ar
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 a2-
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 MIOM1
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 LRP1
localization in Rab11-recycling compartments between 15-30 min
after a2M* stimulation. Then, by TIRF microscopy and LRP1
immunoprecipitation techniques of biotin-labeled cell surface
proteins we showed that a2M* promoted (after 15 min) 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 ina2M*-stimulated cells is
dependent on the endocytic recycling of this receptor
