Article

LIM kinase 1, a key regulator of actin dynamics, is widely expressed in embryonic and adult tissues

Molecular Genetics of Cancer Division, The Walter and Eliza Hall Institute of Medical Research, PO The Royal Melbourne Hospital, Melbourne, Victoria 3050, Australia.
Experimental Cell Research (Impact Factor: 3.37). 05/2004; 294(2):392-405. DOI: 10.1016/j.yexcr.2003.11.024
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ABSTRACT The expression of endogenous LIM kinase 1 (LIMK1) protein was investigated in embryonic and adult mice using a rat monoclonal antibody (mAb), which recognizes specifically the PDZ domain of LIMK1 and not LIMK2. Immunoblotting analysis revealed widespread expression of LIMK1 existing as a 70-kDa protein in tissues and in cell lines, with a higher mass form (approximately 75 kDa) present in some tissues and cell lines. Smaller isoforms of approximately 50 kDa were also occasionally evident. Immunofluorescence analysis demonstrated LIMK1 subcellular localization at focal adhesions in fibroblasts as revealed by co-staining with actin, paxillin and vinculin in addition to perinuclear (Golgi) and occasional nuclear localization. Furthermore, an association between LIMK1 and paxillin but not vinculin was identified by co-immunoprecipitation analysis. LIMK1 is enriched in both axonal and dendritic growth cones of E18 rat hippocampal pyramidal neurons where it is found in punctae that extend far out into filopodia, as well as in a perinuclear region identified as Golgi. In situ, we identify LIMK1 protein expression in all embryonic and adult tissues examined, albeit at different levels and in different cell populations. The rat monoclonal LIMK1 antibody recognizes proteins of similar size in cell and tissue extracts from numerous species. Thus, LIMK1 is a widely expressed protein that exists as several isoforms.

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    • "One factor implicated in regulating the axonal and dendritic outgrowth of neurons in vitro is the cytoplasmic kinase LIM kinase 1 (LIMK1) (Endo et al., 2003; Hsieh et al., 2006; Lee-Hoeflich et al., 2004; Mizuno et al., 1994; Rosso et al., 2004; Tursun et al., 2005). The LIMK1 and LIMK2 proteins are ubiquitously expressed, though LIMK1 is particularly enriched in the brain as well as in the growth cones of cultured neurons (Acevedo et al., 2006; Foletta et al., 2004; Piper et al., 2006; Rosso et al., 2004). LIMK1 directly impacts the assembly of actin filaments in response to modulation of its activity by extrinsic signals (Sarmiere and Bamburg, 2004; Takahashi et al., 2003). "
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    ABSTRACT: The actin cytoskeleton inside extending axonal and dendritic processes must undergo continuous assembly and disassembly. Some extrinsic factors modulate actin turnover through controlling the activity of LIM kinase 1 (LIMK1), which phosphorylates and inactivates the actin depolymerizing factor cofilin. Here, we for the first time examine the function and regulation of LIMK1 in vivo in the vertebrate nervous system. Upon expression of wildtype or kinase-dead forms of the protein, dendrite growth by Xenopus retinal ganglion cells (RGCs) was unchanged. In contrast, maintaining a low, but significant level, of LIMK1 function in the RGC axon is critical for proper extension. Interestingly, bone morphogenetic protein receptor II (BMPRII) is a major regulator of LIMK1 in extending RGC axons, as expression of a BMPRII lacking the LIMK1 binding region caused a dramatic shortening of the axons. Previously, we found that BMPRIIs stimulate dendrite initiation in vivo. Thus, the fact that manipulation of LIMK1 activity failed to alter dendrite growth suggests that BMPs may activate distinct signalling pathways in axons and dendrites.
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    • "In primary cultures of embryonic day 18 (E18) rat hippocampal pyramidal neurons, LIMK1 is found in axons and growth-cone filopodia. In the soma of these neurons , LIMK1 is found in the perinuclear region identified as cis-Golgi (Foletta et al. 2004; Rosso et al. 2004). However, little is known about the expression pattern and cellular localization of the LIMK2 protein. "
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