Electron-microscopical localization of gelsolin in various crustacean muscles

Four paralog gelsolin genes are differentially expressed in the earthworm Lumbricus terrestris

We have identified and characterized four distinct variants of the gelsolin-related protein (EWAM P1-P4) in the earthworm L. terrestris. All of these proteins biochemically qualify as gelsolins since they sever actin filaments in a calcium dependent manner. P1, P2 and P3 are present in the Lumbricus body wall muscle whereas in the gizzard muscle P3 and P4 were found. P1-P4 are encoded by four paralog genes and are differentially expressed in various muscle cell tissues. While the genes for P1 and P2 contain one intron, there was no intron in both P3 and P4 genes. The coding sequences consist of 1104bp (368 amino acids) for P1/P4 and 1101bp (367 amino acids) for P2/P3. Corresponding genes were confirmed by northern blot analysis which revealed three (calculated lengths: 3100, 2300 and 2100 nucleotides) and two (calculated lengths: 2300 and 1700 nucleotides) mRNA transcripts in the body wall and the gizzard, respectively. EWAM mRNA was localized by fluorescence in situ hybridization in the body wall and the gizzard muscle. P1 mRNA was detected in the inner proximal layers of both the circular and longitudinal muscle of the body wall whereas in the gizzard no significant staining was observed for P1. P2-P4 mRNAs were abundant in the outer distal layers of both the circular and the longitudinal muscles of both body wall and gizzard. The differential expression of four paralog gelsolin genes suggests a functional adaptation of different muscle cells with respect to actin filament turnover and modulation of its polymer state.

The interaction of gelsolin with tropomyosin modulates actin dynamics

We have investigated the interactions between the actin-binding proteins gelsolin and tropomyosin, with special respect to any effects on the functional properties of gelsolin. Limited proteolysis indicated that the loop connecting the gelsolin domains G3 and G4 is involved in tropomyosin binding. Under nonpolymerizing conditions, binding of tropomyosin neither prevented the formation of a 2: 1actin-gelsolin complex, nor did it affect the nucleating activity of gelsolin in actin polymerization, likely as a result of competitive displacement of tropomyosin from gelsolin. To evaluate the effect of tropomyosin on the actin filament severing activity of gelsolin, we measured both filamentous actin (F-actin) viscosity and the relative number concentrations of filaments after fragmentation, either by gelsolin alone or by gelsolin-tropomyosin complexes. The interaction of gelsolin with tropomyosin caused a reduction in F-actin severing activity of up to 80% compared to gelsolin alone. Thus, being bound to gelsolin, tropomyosin prevented gelsolin from severing actin filaments. By contrast, the severing activity of gelsolin for F-actin/tropomyosin was similar to that for F-actin alone even at a tropomyosin : actin saturation ratio of 1: 7. Thus, when bound to actin filaments, tropomyosin did not significantly inhibit the severing of filaments by gelsolin. The interaction between gelsolin and tropomyosin was largely independent of the muscle actin and tropomyosin isoforms investigated. The results obtained in the present study suggest that tropomyosin is involved in the modulation of actin dynamics not via the protection of filaments against severing, but rather by binding gelsolin in solution to prevent it from severing and to promote the formation of new actin filaments.

Actin-binding Rho activating protein is expressed in the central nervous system of normal adult rats

Previous studies show that actin-binding Rho activating protein (Abra) is expressed in cardiomyocytes and vascular smooth muscle cells. In this study, we investigated the expression profile of Abra in the central nervous system of normal adult rats by confocal immunofluorescence. Results showed that Abra immunostaining was located in neuronal nuclei, cytoplasm and processes in the central nervous system, with the strongest staining in the nuclei; in the cerebral cortex, Abra positive neuronal bodies and processes were distributed in six cortical layers including molecular layer, external granular layer, external pyramidal layer, internal granular layer, internal pyramidal layer and polymorphic layer; in the hippocampus, the cell bodies of Abra positive neurons were distributed evenly in pyramidal layer and granular layer, with positive processes in molecular layer and orien layer; in the cerebellar cortex, Abra staining showed the positive neuronal cell bodies in Purkinje cell layer and granular layer and positive processes in molecular layer; in the spinal cord, Abra-immunopositive products covered the whole gray matter and white matter; co-localization studies showed that Abra was co-stained with F-actin in neuronal cytoplasm and processes, but weakly in the nuclei. In addition, in the hippocampus, Abra was co-stained with F-actin only in neuronal processes, but not in the cell body. This study for the first time presents a comprehensive overview of Abra expression in the central nervous system, providing insights for further investigating the role of Abra in the mature central nervous system.

Proteomic analysis of serum proteins in acute ischemic stroke patients treated with acupuncture

In the present study, we have investigated the effects of acupuncture on (1) serum protein expression that might have a beneficial effect on stroke patients and (2) the strength of limb muscles in stroke patients. A total of 35 acute ischemic stroke (IS) patients were divided into two groups, one receiving drug treatment alone and the other receiving electroacupuncture (EA) and drug treatment. EA treatment was performed on eight acupuncture points once a day for 10 consecutive days. Serum proteins were detected using a proteomics method based on two-dimensional gel electrophoresis, and the specificity of proteins was confirmed by Western blotting. Changes of limb muscle strength were measured using a modified Medical Research Council grading scale. After EA, SerpinG1 protein expression in serum was down-regulated while the expressions of gelsolin, complement component I, C3, C4B and beta-2-glycoprotein I proteins were up-regulated in patients. The changes of serum protein expression were further confirmed by Western blotting in a majority of the cases. The muscle strength of limbs was increased after EA in 18 patients. EA appears to be effective in regulating differential expression of multiple serum proteins involved in stroke, and also in enhancement of muscle strength recovery in acute IS patients despite an individual variation.