LIM kinase 1, a key regulator of actin dynamics, is widely expressed in embryonic and adult tissues.
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.
- SourceAvailable from: PubMed Central[Show abstract] [Hide abstract]
ABSTRACT: LIM kinases (LIMKs) are important cell cytoskeleton regulators that play a prominent role in cancer manifestation and neuronal diseases. The LIMK family consists of two homologues, LIMK1 and LIMK2, which differ from one another in expression profile, intercellular localization, and function. The main substrate of LIMK is cofilin, a member of the actin-depolymerizing factor (ADF) protein family. When phosphorylated by LIMK, cofilin is inactive. LIMKs play a contributory role in several neurodevelopmental disorders and in cancer growth and metastasis. We recently reported the development and validation of a novel LIMK inhibitor, referred to here as T56-LIMKi, using a combination of computational methods and classical biochemistry techniques. Here we report that T56-LIMKi inhibits LIMK2 with high specificity, and shows little or no cross-reactivity with LIMK1. We found that T56-LIMKi decreases phosphorylated cofilin (p-cofilin) levels and thus inhibits growth of several cancerous cell lines, including those of pancreatic cancer, glioma and schwannoma. Because the most promising in-vitro effect of T56-LIMKi was observed in the pancreatic cancer cell line Panc-1, we tested the inhibitor on a nude mouse Panc-1 xenograft model. T56-LIMKi reduced tumor size and p-cofilin levels in the Panc-1 tumors, leading us to propose T56-LIMKi as a candidate drug for cancer therapy.Oncoscience. 01/2014; 1(1):39-48.
- [Show abstract] [Hide abstract]
ABSTRACT: Changes in the actin cytoskeleton in neurons are associated with synaptic plasticity and may also be involved in mechanisms of nociception. We found that the LIM motif-containing protein kinases (LIMKs), which regulate actin dynamics, promoted the development of inflammatory hyperalgesia (excessive sensitivity to painful stimuli). Pain is sensed by the primary sensory neurons of dorsal root ganglion (DRG). In rats injected with complete Freund's adjuvant (CFA), which induces inflammatory heat hyperalgesia, DRG neurons showed an increase in LIMK activity and in the phosphorylation and thus inhibition of the LIMK substrate cofilin, an actin-severing protein. Manipulations that reduced LIMK activity or abundance, prevented the phosphorylation of cofilin, or disrupted actin filaments in DRG neurons attenuated CFA-induced heat hyperalgesia. Inflammatory stimuli stimulated actin polymerization and enhanced the response of the cation channel TRPV1 (transient receptor potential V1) to capsaicin in DRG neurons, effects that were reversed by the knockdown of LIMK or preventing cofilin phosphorylation. Furthermore, inflammatory stimuli caused the serine phosphorylation of TRPV1, which was abolished by preventing cofilin phosphorylation in DRG neurons. We conclude that LIMK-dependent actin rearrangement in primary sensory neurons, leading to altered TRPV1 sensitivity, is involved in the development of inflammatory hyperalgesia.Science Signaling 06/2014; 7(331):ra61. · 7.65 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Coordinated actin microfilament and microtubule dynamics are required for salivary gland development, although the mechanisms by which they contribute to branching morphogenesis are not defined. Since LIMK regulates both actin and microtubule organization, we investigated the role of LIMK signaling in mouse embryonic submandibular salivary glands using ex-vivo organ cultures. Both LIMK 1 and 2 were necessary for branching morphogenesis and functioned to promote epithelial early and late-stage cleft progression through regulation of both microfilaments and microtubules. LIMK-dependent regulation of these cytoskeletal systems was required to control focal adhesion-dependent fibronectin assembly and integrin β1 activation, involving the LIMK effectors, cofilin and TPPP/p25, for assembly of the actin and tubulin-based cytoskeletal systems, respectively. We demonstrate that LIMK regulates the early stages of cleft formation - cleft initiation, stabilization, and progression, via establishment of actin stability. Further, we reveal a novel role for the microtubule assembly factor, p25, in regulating stabilization and elongation of late-stage progressing clefts. This study demonstrates the existence of multiple actin- and microtubule-dependent stabilization steps that are controlled by LIMK and are required in cleft progression during branching morphogenesis.Molecular Biology of the Cell 06/2014; · 4.55 Impact Factor