Collapsin response mediator protein-4 regulates F-actin bundling

• Published in: Experimental cell research Vol. 310; no. 2; pp. 434 - 444
• Main Authors: Rosslenbroich, Volker, Dai, Lingsong, Baader, Stephan L., Noegel, Angelika A., Gieselmann, Volkmar, Kappler, Joachim
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.2005; Elsevier BV
• Subjects: Actins - analysis; Actins - metabolism; Animals; Cell Movement; Cytosol - chemistry; Green Fluorescent Proteins - analysis; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; Humans; Nerve Tissue Proteins - analysis; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Pseudopodia - chemistry; Rats; Recombinant Fusion Proteins - analysis; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; RNA, Small Interfering - pharmacology; Transcriptional Activation; Transfection; Tumor Cells, Cultured; ADF; LatA; arp2/3; ICC; GSK-3; WB; CRMP; CB
• ISSN: 0014-4827; 1090-2422
• DOI: 10.1016/j.yexcr.2005.08.005

Collapsin response mediator proteins (CRMPs) form a family of cytosolic phosphoproteins which are involved in the signal transduction of semaphorin 3A leading to growth cone collapse. These proteins interact with a variety of cytosolic proteins including tubulin heterodimers. Here, we show that CRMP-4 co-localizes with F-actin in regular rib-like structures within lamellipodia of B35 neuroblastoma cells. Furthermore, depolymerization of actin fibers changed the distribution of GFP-CRMP-4 in vivo. In vitro, recombinant CRMP-4 formed homo-oligomers, bound to F-actin and organized F-actin into tight bundles. Both oligomerization and F-actin bundling depended on the C-terminal part of CRMP-4. The stoichiometry of actin and CRMP-4 in bundles was approximately 1:1 and the apparent equilibrium constant of the microfilament–CRMP-4 interaction was estimated from bundling assays as K (app) = 730 mM −1. CRMP-4 was abundant in the cytosol of B35 neuroblastoma cells and its concentration was measured as ≈1.7 μM. Overexpression of CRMP-4 inhibited the migration of B35 neuroblastoma cells, while knockdown of CRMP-4 enhanced cell migration and disturbed rib-like actin-structures in lamellipodia. Taken together, our data indicate that CRMP-4 promotes bundling of F-actin in vitro, that it is an important component of rib-like actin bundles in lamellipodia in vivo and that it functionally regulates the actin cytoskeleton in motile cells. These findings suggest a specific regulatory role of CRMP-4 towards the actin cytoskeleton which may by be relevant for growth cone collapse.