Two distinct mechanisms target membrane proteins to the axonal surface.
We have investigated the trafficking of two endogenous axonal membrane proteins, VAMP2 and NgCAM, in order to elucidate the cellular events that underlie their polarization. We found that VAMP2 is delivered to the surface of both axons and dendrites, but preferentially endocytosed from the dendritic membrane. A mutation in the cytoplasmic domain of VAMP2 that inhibits endocytosis abolished its axonal polarization. In contrast, the targeting of NgCAM depends on sequences in its ectodomain, which mediate its sorting into carriers that preferentially deliver their cargo proteins to the axonal membrane. These observations show that neurons use two distinct mechanisms to polarize proteins to the axonal domain: selective retention in the case of VAMP2, selective delivery in the case of NgCAM.
Sampo
Bernard
B
Center for Research on Occupational and Environmental Toxicology, Oregon Health and Science University, Portland, OR 97239, USA.
Kaech
Stefanie
S
Kunz
Stefan
S
Banker
Gary
G
D020816:Amino Acid Motifs / Q000502:physiology; D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure; D019062:Cell Adhesion Molecules, Neuron-Glia / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D003712:Dendrites / Q000378:metabolism / Q000648:ultrastructure; D004705:Endocytosis / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D050683:R-SNARE Proteins; D051381:Rats
D019062:Cell Adhesion Molecules, Neuron-Glia; D008565:Membrane Proteins; D050683:R-SNARE Proteins