Drebrin preserves endothelial integrity by stabilizing nectin at adherens junctions.

Regulation of cell-cell contacts is essential for integrity of the vascular endothelium. Here, a critical role of the F-actin-binding protein drebrin in maintaining endothelial integrity is revealed under conditions mimicking vascular flow. Drebrin knockdown leads to weakening of cell-cell contacts, characterized by loss of nectin from adherens junctions and its subsequent lysosomal degradation. Immunoprecipitation, FRAP and mitochondrial re-targeting experiments show that nectin stabilization occurs through a chain of interactions: drebrin binding to F-actin, interaction of drebrin and afadin through their polyproline and PR1-2 regions, and recruitment of nectin through the PDZ region of afadin. Key elements are modules in drebrin that confer binding to afadin and F-actin. Evidence for this was obtained using constructs containing the PDZ region of afadin coupled to the F-actin-binding region of drebrin or to lifeact, which restore junctional nectin under knockdown of drebrin or of both drebrin and afadin. Drebrin, containing binding sites for both afadin and F-actin, is thus uniquely equipped to stabilize nectin at endothelial junctions and to preserve endothelial integrity under vascular flow.

Zona occludens proteins modulate podosome formation and function.

Podosomes are highly dynamic structures that are involved in cell adhesion and extracellular matrix remodeling. They present as intracellular columns composed of an actin-rich core region and a surrounding ring-like structure containing focal adhesion proteins, actin binders as well as cell signaling molecules. A key player in podosome biogenesis is the scaffolding protein cortactin, which is thought to control actin assembly at the core region. We show that the zona occludens protein 1 (ZO-1), a pivotal tight junction protein and known binding partner of cortactin, is a component of podosomes. In the smooth muscle cell line A7r5, phorbol ester treatment induced a rapid relocation of ZO-1 from the cell cortex and cytosolic pools toward newly formed podosomes. Podosomal localization was also observed for the known ZO-1-binding proteins l-afadin, α-catenin, and phospho-connexin 43. Truncation studies revealed that the actin-binding domain but not the association with cortactin is necessary for ZO-1 recruitment to podosomes. Moreover, impaired ZO-1 expression leads to significantly reduced podosome formation and concomitant decreased matrix degradation at podosomes. Our findings demonstrate that besides their known function in tight junction assembly and intercellular communication, zona occludens proteins and their binding partners may play a novel role in podosome formation and associated function, thus regulating cell adhesion and matrix remodeling.

The Rationale for Exercise in the Management of Pain in Parkinson's Disease.

Pain is a distressing non-motor symptom experienced by up to 85% of people with Parkinson's disease (PD), yet it is often untreated. This pain is likely to be influenced by many factors, including the disease process, PD impairments as well as co-existing musculoskeletal and/or neuropathic pain conditions. Expert opinion recommends that exercise is included as one component of pain management programs; however, the effect of exercise on pain in this population is unclear. This review presents evidence describing the potential influence of exercise on the pain-related pathophysiological processes present in PD. Emerging evidence from both animal and human studies suggests that exercise might contribute to neuroplasticity and neuro-restoration by increasing brain neurotrophic factors, synaptic strength and angiogenesis, as well as stimulating neurogenesis and improving metabolism and the immune response. These changes may be beneficial in improving the central processing of pain. There is also evidence that exercise can activate both the dopaminergic and non-dopaminergic pain inhibitory pathways, suggesting that exercise may help to modulate the experience of pain in PD. Whilst clinical data on the effects of exercise for pain relief in people with PD are scarce, and are urgently needed, preliminary guidelines are presented for exercise prescription for the management of central neuropathic, peripheral neuropathic and musculoskeletal pain in PD.

Lasp-1 regulates podosome function.

Eukaryotic cells form a variety of adhesive structures to connect with their environment and to regulate cell motility. In contrast to classical focal adhesions, podosomes, highly dynamic structures of different cell types, are actively engaged in matrix remodelling and degradation. Podosomes are composed of an actin-rich core region surrounded by a ring-like structure containing signalling molecules, motor proteins as well as cytoskeleton-associated proteins. Lasp-1 is a ubiquitously expressed, actin-binding protein that is known to regulate cytoskeleton architecture and cell migration. This multidomain protein is predominantely present at focal adhesions, however, a second pool of Lasp-1 molecules is also found at lamellipodia and vesicle-like microdomains in the cytosol.In this report, we show that Lasp-1 is a novel component and regulator of podosomes. Immunofluorescence studies reveal a localization of Lasp-1 in the podosome ring structure, where it colocalizes with zyxin and vinculin. Life cell imaging experiments demonstrate that Lasp-1 is recruited in early steps of podosome assembly. A siRNA-mediated Lasp-1 knockdown in human macrophages affects podosome dynamics as well as their matrix degradation capacity. In summary, our data indicate that Lasp-1 is a novel component of podosomes and is involved in the regulation of podosomal function.

Structural and functional diversity of novel coronin 1C (CRN2) isoforms in muscle.

Coronin 1C (synonyms: coronin-3, CRN2), a WD40 repeat-containing protein involved in cellular actin dynamics, is ubiquitously expressed in human tissues. Here, we report on the identification and functional characterization of two novel coronin 1C isoforms, referred to as CRN2i2 and CRN2i3, which also associate with F-actin. Analyses of the coronin 1C gene disclosed a single promoter containing binding sites for myogenic regulatory factors and an alternative first exon 1b present in intron 1, which give rise to the novel isoforms. Chromatin immunoprecipitation studies demonstrate MyoD binding to a region of the CRN2 gene, which contains a highly conserved E-box element in exon 1a. Gel-filtration assays suggest that the largest isoform 3 exists as a monomer, in contrast to isoform 1 and isoform 2 appearing as trimers. CRN2i3, which can be induced by MyoD, is exclusively expressed in well-differentiated myoblasts as well as in mature skeletal muscle tissue. In human skeletal muscle, CRN2i3 is a novel component of postsynaptic neuromuscular junctions and thin filaments of myofibrils. Together, our findings postulate a role for CRN2 isoforms in the structural and functional organization of F-actin in highly ordered protein complexes.