Clathrin assembly protein AP180 and CALM differentially control axogenesis and dendrite outgrowth in embryonic hippocampal neurons.
Emerging data suggest that, much like epithelial cells, the polarized growth of neurons requires both the secretory and endocytic pathways. The clathrin assembly proteins AP180 and CALM (clathrin assembly lymphoid myeloid protein) are known to be involved in clathrin-mediated endocytosis, but their roles in mammalian neurons and, in particular, in developmental processes before synaptogenesis are unknown. Here we provide evidence that AP180 and CALM play critical roles in establishing the polarity and controlling the growth of axons and dendrites in embryonic hippocampal neurons. Knockdown of AP180 primarily impairs axonal development, whereas reducing CALM levels results in dendritic dystrophy. Conversely, neurons that overexpress AP180 or CALM generate multiple axons. Ultrastructural analysis shows that CALM affiliates with a wider range of intracellular trafficking organelles than does AP180. Functional analysis shows that endocytosis is reduced in both AP180-deficient and CALM-deficient neurons. Additionally, CALM-deficient neurons show disrupted secretory transport. Our data demonstrate previously unknown functions for AP180 and CALM in intracellular trafficking that are essential in the growth of neurons.
Laboratory of Neurosciences, National Institute on Aging-National Institutes of Health, Baltimore, Maryland 21224, USA.
Ittai
I
Bushlin
Ronald S
RS
Petralia
Fangbai
F
Wu
Asaff
A
Harel
Mohamed R
MR
Mughal
Mark P
MP
Mattson
Pamela J
PJ
Yao
D000818:Animals; D001369:Axons / Q000502:physiology*; D016764:Cell Polarity / Q000502:physiology; D002478:Cells, Cultured; D003712:Dendrites / Q000502:physiology*; D004705:Endocytosis / Q000502:physiology; D017353:Gene Deletion; D006624:Hippocampus / Q000166:cytology / Q000196:embryology*; D008854:Microscopy, Electron; D034041:Monomeric Clathrin Assembly Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D015388:Organelles / Q000378:metabolism; D051381:Rats; D014018:Tissue Distribution; D015854:Up-Regulation; D050988:Vesicle-Associated Membrane Protein 2 / Q000378:metabolism
D034041:Monomeric Clathrin Assembly Proteins; C499980:Picalm protein, rat; C494706:Vamp2 protein, rat; D050988:Vesicle-Associated Membrane Protein 2; C439023:clathrin assembly protein AP180