The TC10-Exo70 complex is essential for membrane expansion and axonal specification in developing neurons.
Axonal elongation is one of the hallmarks of neuronal polarization. This phenomenon requires axonal membrane growth by exocytosis of plasmalemmal precursor vesicles (PPVs) at the nerve growth cone, a process regulated by IGF-1 activation of the PI3K (phosphatidylinositol-3 kinase) pathway. Few details are known, however, about the targeting mechanisms for PPVs. Here, we show, in cultured hippocampal pyramidal neurons and growth cones isolated from fetal rat brain, that IGF-1 activates the GTP-binding protein TC10, which triggers translocation to the plasma membrane of the exocyst component exo70 in the distal axon and growth cone. We also show that TC10 and exo70 function are necessary for addition of new membrane and, thus, axon elongation stimulated by IGF-1. Moreover, expression silencing of either TC10 or exo70 inhibit the establishment of neuronal polarity by hindering the insertion of IGF-1 receptor in one of the undifferentiated neurites. We conclude that, in hippocampal pyramidal neurons in culture, (1) membrane expansion at the axonal growth cone is regulated by IGF-1 via a cascade involving TC10 and the exocyst complex, (2) TC10 and exo70 are essential for the polarized externalization of IGF-1 receptor, and (3) this process is necessary for axon specification.
Departamento de Química Biológica y Centro de Investigaciones en Química Biológica de Córdoba, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba-Consejo Nacional de Investigaciones Científicas y Técnicas, 5000 Córdoba, Argentina.
Sebastián
S
Dupraz
Diego
D
Grassi
María Eugenia
ME
Bernis
Lucas
L
Sosa
Mariano
M
Bisbal
Laura
L
Gastaldi
Ignacio
I
Jausoro
Alfredo
A
Cáceres
Karl H
KH
Pfenninger
Santiago
S
Quiroga
D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure*; D002478:Cells, Cultured; D022082:Cellular Structures / Q000187:drug effects / Q000378:metabolism; D002867:Chromones / Q000494:pharmacology; D004622:Embryo, Mammalian; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus / Q000166:cytology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009025:Morpholines / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D017966:Pyramidal Cells / Q000166:cytology*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017526:Receptor, IGF Type 1 / Q000502:physiology; D013997:Time Factors; D014162:Transfection / Q000379:methods; D033921:Vesicular Transport Proteins / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
D002867:Chromones; D004791:Enzyme Inhibitors; C109901:Exoc7 protein, rat; D009025:Morpholines; D034741:RNA, Small Interfering; D033921:Vesicular Transport Proteins; D049452:Green Fluorescent Proteins; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; C503262:Rhoq protein, rat; D020741:rho GTP-Binding Proteins