{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Lim Kinase ans Slingshoot induce neurite growth

Lim Kinase ans Slingshoot induce neurite growth -...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
LIM Kinase and Slingshot Are Critical for Neurite Extension * S Received for publication,November 27, 2006, and in revised form, February 5, 2007 Published, JBC Papers in Press,March 13, 2007, DOI 10.1074/jbc.M610873200 Mitsuharu Endo, Kazumasa Ohashi, and Kensaku Mizuno 1 From the Department of Biomolecular Sciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan 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 com- pletely inhibited NGF-induced neurite extension from PC12 cells, and double knockdown of SSH1/SSH2 significantly sup- pressed 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 activi- ties 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. The regulation of actin cytoskeleton dynamics plays a funda- mental role in cell shape change, motility, and migration in response to stimuli. In neurons, actin filaments accumulate at the distal tip of the growth cone in the growing neurite, and actin filament dynamics and reorganization are essential for controlling growth cone motility and morphology and deter- mining the direction and speed of neurite extension (1–4). Cofilin and its closely related protein, actin depolymerizing fac- tor (ADF), 2 are key mediators of actin filament dynamics that act by stimulating the depolymerization and severing of actin filaments (5). The activities of cofilin and ADF are inhibited by phosphorylation at Ser-3 by LIM kinases (LIMKs, composed of LIMK1 and LIMK2) (6, 7) and TES kinases (TESKs, composed of TESK1 and TESK2) (8); the inactive Ser-3-phosphorylated cofilin and ADF (P-cofilin/P-ADF) are reactivated by dephos- phorylation by Slingshot (SSH) family protein phosphatases (SSH1, SSH2, and SSH3) (9, 10) and chronophin (a haloacid dehalogenase) (11). Because cofilin/ADF and their upstream regulators, LIMKs and SSHs, are abundant in neuronal growth cones (12–15), these proteins have been implicated in the con-
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern