Cellular and Molecular Neurobiology
Author: María Belén Montiel | Email: bmontiel@iib.unsam.edu.ar
María Belén Montiel1°, Beata Fuchsova1°
1° Instituto de Investigaciones Biotecnológicas, EByN, UNSAM-CONICET
Gpm6a is a neuronal membrane glycoprotein with four transmembrane domains and the
N- and C-terminal ends facing the cytoplasm. It functions in the processes of neuronal
development and its overexpression leads to the extensive formation of filopodia. However, the
mechanism of its action is not clearly understood.
Previously, we have identified E258 residue within the C-terminus of Gpm6a as a critical
for the process of filopodium formation. Moreover, we observed that the incapacity of E258A
Gpm6a to form filopodia correlates with its accumulation in the cytoplasm of neuroblastoma N2a
cells. Subsequent bioinformatic analysis revealed that E258 is predicted as a part of sorting signal
of transmembrane proteins. Since the endocytic sorting and recycling of membrane proteins has
been shown to assist plasma membrane remodeling necessary for different types of membrane
outgrowth, we asked here whether the endocytic fate of Gpm6a is affected by the mutation that
impact filopodium outgrowth. Using confocal microscopy we analyzed the effect of E258A
overexpression on endocytic trafficking of Gpm6a in primary hippocampal neurons. We observed
that the overexpression of E258A not only leads to the decreased neuronal arborization as
assessed by Sholl analysis but also to the differences in the colocalization of Gpm6a with both
recycling (Rab 11 positive) and degradative (Lamp1-positive) compartments.