LIM kinase and slingshot are critical for neurite extension.
Cofilin and its closely related protein, actin-depolymerizing factor (ADF), are key regulators of actin cytoskeleton dynamics that have been implicated in growth cone motility and neurite extension. Cofilin/ADF are inactivated by LIM kinase (LIMK)-catalyzed phosphorylation and reactivated by Slingshot (SSH)-catalyzed dephosphorylation. Here we examined the roles of cofilin/ADF, LIMKs (LIMK1 and LIMK2), and SSHs (SSH1 and SSH2) in nerve growth factor (NGF)-induced neurite extension. Knockdown of cofilin/ADF by RNA interference almost completely inhibited NGF-induced neurite extension from PC12 cells, and double knockdown of SSH1/SSH2 significantly suppressed both NGF-induced cofilin/ADF dephosphorylation and neurite extension from PC12 cells, thus indicating that cofilin/ADF and their activating phosphatases SSH1/SSH2 are critical for neurite extension. Interestingly, NGF stimulated the activities of both LIMK1 and LIMK2 in PC12 cells, and suppression of LIMK1/LIMK2 expression or activity significantly reduced NGF-induced neurite extension from PC12 cells or chick dorsal root ganglion (DRG) neurons. Inhibition of LIMK1/LIMK2 activity reduced actin filament assembly in the peripheral region of the growth cone of chick DRG neurons. These results suggest that proper regulation of cofilin/ADF activities through control of phosphorylation by LIMKs and SSHs is critical for neurite extension and that LIMKs regulate actin filament assembly at the tip of the growth cone.
Endo
Mitsuharu
M
Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan.
Ohashi
Kazumasa
K
Mizuno
Kensaku
K
D008841:Actin Cytoskeleton / Q000378:metabolism; D051339:Actin Depolymerizing Factors / Q000235:genetics / Q000378:metabolism; D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002645:Chickens; D051345:Destrin / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D005727:Ganglia, Spinal / Q000166:cytology / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology*; D020439:Growth Cones / Q000201:enzymology; D054461:Lim Kinases; D020932:Nerve Growth Factor / Q000494:pharmacology; D016501:Neurites / Q000201:enzymology*; D016716:PC12 Cells; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000096:biosynthesis* / Q000235:genetics; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000502:physiology*; D051381:Rats
D051339:Actin Depolymerizing Factors; D000199:Actins; D051345:Destrin; D020932:Nerve Growth Factor; D011494:Protein Kinases; D054461:Lim Kinases; C515894:Limk1 protein, rat; C490644:Limk2 protein, rat; D010749:Phosphoprotein Phosphatases