Chronophin coordinates cell leading edge dynamics by controlling active cofilin levels

Abstract

Cofilin, a critical player of actin dynamics, is spatially and temporally regulated to control the direction and force of membrane extension required for cell locomotion. In carcinoma cells, although the signaling pathways regulating cofilin activity to control cell direction have been established, the molecular machinery required to generate the force of the protrusion remains unclear. We show that the cofilin phosphatase chronophin (CIN) spatiotemporally regulates cofilin activity at the cell edge to generate persistent membrane extension. We show that CIN translocates to the leading edge in a PI3-kinase-, Rac1-, and cofilindependent manner after EGF stimulation to activate cofilin, promotes actin free barbed end formation, accelerates actin turnover, and enhances membrane protrusion. In addition, we establish that CIN is crucial for the balance of protrusion/retraction events during cell migration. Thus, CIN coordinates the leading edge dynamics by controlling active cofilin levels to promote MTLn3 cell protrusion.ofilin is one crucial mediator of actin cytoskeletal dynamics during cell motility (1-5). At the cell edge, cofilin severs F-actin filaments, generating substrates for Arp2/3-mediated branching activity and contributing to F-actin depolymerization by creating a new pointed end and F-actin assembly by increasing the pool of polymerization-competent actin monomers (G-actin) (6, 7). Because of its ability to sever actin filaments and thus, modulate actin dynamics, the precise spatial and temporal regulation of cofilin activity at the cell leading edge is crucial to cell protrusion, chemotaxis, and motility both in vitro and in vivo (2,(8)(9)(10)(11)(12)(13). Misregulation of cofilin activity and/or expression is directly related to diseases, including tumor metastasis (14-18) and Alzheimer's disease (19).Several mechanisms regulate tightly the activation of cofilin in response to upstream stimuli, including interaction with phosphatidylinositol (4,5)-bisphosphate (20-22), local pH changes (23,24), and phosphorylation at a single regulatory serine (Ser3) (8,25). The phosphorylation of cofilin, leading to its inactivation, is catalyzed by two kinase families: the LIM-kinases [LIMKs(Lin11, Isl-1, and Mec-3 domain)] and the testicular kinases (25-27). Two primary families of ser/thr phosphatases dephosphorylate and reactivate the actin-depolymerizing and -severing functions of cofilin: slingshot (SSH) (28) and chronophin (CIN) (29).SSH was identified as a cofilin phosphatase through genetic studies in Drosophila (28). The most active and abundant SSH isoform, SSH-1L, has been implicated in such biological processes as cell division, growth cone motility/morphology, neurite extension, and actin dynamics during membrane protrusion (30). SSH dephosphorylates a number of actin regulatory proteins in addition to cofilin, including LIMK1 (31) and Coronin 1B (32). CIN is a haloacid dehydrogenase-type phosphatase, a family of enzymes with activity in mammalian cells that has been poorly characterized. CIN dephosph...

Cofilin: A Promising Protein Implicated in Cancer Metastasis and Apoptosis

“…PP1/PP2A is a direct upstream regulator of Cofilin dephosphorylation activation (Ambach et al, 2000 ; Eichhorn et al, 2009 ). Increased expression of PP1/PP2A phosphatase can promote cofilin dephosphorylation activation (Delorme-Walker et al, 2015 ). Then the dephosphorylated cofilin translocates to the outer membrane of the mitochondria to bind directly to F-actin, and depolymerize the F-actin into G-actin, causing the mitosis of the mitochondria.…”

Actin dynamics and cofilin‐actin rods in alzheimer disease

“…Peroxide has been recognized for some time as a second messenger in cell migration [Forman et al, ], although previous work suggested that exogenous peroxide stimulated cell protrusion efficiency through increased cofilin activity and free actin barbed‐end formation [Taulet et al, ]. Further work is needed to clarify if there are differentially regulated pools of cofilin, one of which is subjected to oxidative inhibition and the other to activation, perhaps through CIN regulated dephosphorylation [Delorme‐Walker et al, ].…”

ROCK1 activation-mediated mitochondrial translocation of Drp1 and cofilin are required for arnidiol-induced mitochondrial fission and apoptosis

“…Dephosphorylation of Ser3 leads to cofilin activation [14]. The main protein phosphatases known to activate cofilin are serine/threonine phosphatases type 1 (PP1) and type 2A (PP2A), slingshot (SSH), and chronophin [14][15][16].…”