A Neurally Enriched Coronin-like Protein, ClipinC, Is a Novel Candidate for an Actin Cytoskeleton-Cortical Membrane-linking Protein

Abstract

Brain-enriched human FC96 protein shows a close sequence similarity to the Dictyostelium actin-binding protein coronin, which has been implicated in cell motility, cytokinesis, and phagocytosis. A phylogenetic tree analysis revealed that FC96 and two other mammalian molecules (p57 and IR10) form a new protein family, the coronin-like protein (Clipin) family; thus hereafter we refer to FC96 as ClipinC. A WD domain and a succeeding ␣-helical region are conserved among coronin and Clipin family members. ClipinC is predominantly expressed in the brain, and discrete areas in the mouse brain were intensely labeled with anti-ClipinC antibodies. ClipinC was also shown to bind directly to F-actin in vitro. Immunocytochemical analysis revealed that ClipinC accumulated at focal adhesions as well as at neurite tips and stress fibers. Furthermore, ClipinC was associated with vinculin, which is a major component of focal contacts. These results indicate that ClipinC is also a component part of the cross-bridge between the actin cytoskeleton and the plasma membrane. These findings and the previously reported function of coronin suggest that ClipinC may play specific roles in the reorganization of neuronal actin structure, a change that has been implicated in both cell motility and growth cone advance.Actin filaments in neuronal cells form a cortical framework that helps to localize membrane proteins, and F-actin dynamics has been implicated in directing neuronal outgrowth. Rearrangement of the actin cytoskeleton occurs in response to various stimuli such as soluble factors or attachment to a substratum (1, 2). The regulation of F-actin patterns involves actin polymerization and actin cross-linking. Factors regulating these processes communicate with the small G proteins of the Rho family (3) and the phosphatidylinositol metabolism system (4), both of which are triggered by extracellular cues through a variety of receptors.The Dictyostelium actin-binding protein coronin was first purified from an actin-myosin complex and was hypothesized to transmit signals from the membrane receptors to the cortical cytoskeleton (5). Coronin accumulates at the leading edges of moving cells and in crown-shaped extensions on the dorsal cell surface. The involvement of coronin in cell motility, cytokinesis, and phagocytosis, all of which depend on cytoskeletal rearrangement, has been demonstrated by use of a gene replacement mutant. In a mutant that lacks coronin, cell motility is reduced to less than half of the normal speed, and cytoplasmic cleavage in cytokinesis is impaired (6). Further, in the coronin null (cor Ϫ ) mutant, the rate of yeast uptake is reduced by about 70% (7). However, the distribution of actin filaments in cor Ϫ cells is similar to that in the wild-type ones (6).In this study, we found a novel candidate for an actin cytoskeleton-cortical membrane linking protein; this protein, ClipinC, is also the third member of a family of mammalian homologs of Dictyostelium coronin. The ClipinC transcript was predominantly expressed in th...

A 4 bp deletion mutation in DLX3 enhances osteoblastic differentiation and bone formation in vitro

“…More importantly, C2C12 cells stably transfected with MT-DLX3 cDNA increased the expression levels of Runx2 and osterix protein when these cells were cultured with osteogenic media for more than 6 days suggesting that MT-DLX3 also enhanced the osteoblastic differentiation of C2C12 cells. In addition to desmin, expression levels of vimentin and tubulin alpha2, intermediate filament components in muscle structure formation [36] and vinculin, involved in cell adhesion in the attachment of the actin-based microfilaments to the plasma membrane, [37] are also down-regulated in C2C12 cells transfected with the MT-DLX3 (Table 1). However, transient transfection of MT-DLX3 into C2C12 cells did not markedly down-regulated desmin or MyoD expression suggesting that temporal expression of MT-DLX3 in C2C12 cells for 3 days might not be enough to change the phenotype of mesenchymal C2C12 cells to osteoblastic precursors.…”

In Vivo and in Vitro Characterization of Novel Neuronal Plasticity Factors Identified following Spinal Cord Injury

“…28). Analogs of Coronin 1b (cilpin C) and a Rab family member (Rab8) have also been localized at cellular protrusions, and neurite tips in PC-12 and SH-SY5 cells (29,30). Therefore, based upon their temporal co-regulation with the other members of the cluster, and upon their known or putative biological function, Coronin 1b, and Rab13 appeared to be factors involved in neurite outgrowth and differentiation.…”

“…38). Importantly, cilpin C, a human Coronin-like homolog protein, which is highly expressed in brain, has been identified in stress fibers and neurite tips in SH-SY5 neuronal cells during neurite outgrowth (29).…”

Ezrin silencing remodulates the expression of Phosphoinositide‐specific Phospholipase C enzymes in human osteosarcoma cell lines

“…Once activated, Ezrin, commonly localized in the cytoplasm in its inactive form, moves and tethers actin to the cortical membrane, thus promoting cytoskeleton reorganization and subsequent cell morphology alterations (Dard et al 2004;Zhu et al 2007;Di Cristofano et al 2010;Yang et al 2012;Zhao et al 2011;Tan and Yang 2010). Beside phosphorylation, activation of ERM proteins also occurs after interaction with PIP2 (Gilmore and Burridge 1996, Hirao et al 1996, Legg and Isacke 1998, Nakamura et al 1999. The levels of PIP2 are regulated by means of the PI-specific Phospholipase C family of enzymes Berridge and Dupont (1994); Divecha and Irvine 1995;Hisatsune et al 2005;Rhee 2001Bunney andKatan 2011).…”

“…The role of Ezrin in actin assembly (Defacque et al 2000, Defacque et al 2002 largely depends on the membrane PIP2 levels (Hao et al 2009). ERM proteins bind actin and, by means of their N-terminal domains, simultaneously the PIP2 located at the plasma membrane (Niggli, V et al 2008, Gilmore and Burridge 1996Isenberg and Niggli 1998, Nakamura et al 1999, Eberle et al 1990, Dobos et al 1992, Apgar 1995, Gachet et al 1997, Gratacap et al 1998. Once activated, Ezrin, commonly localized in the cytoplasm in its inactive form, moves and tethers actin to the cortical membrane, thus promoting cytoskeleton reorganization and subsequent cell morphology alterations (Dard et al 2004;Zhu et al 2007;Di Cristofano et al 2010;Yang et al 2012;Zhao et al 2011;Tan and Yang 2010).…”