Control of Cytoplasmic Actin Gel-Sol Transformation by Gelsolin, A Calcium-Dependent Regulatory Protein
(Impact Factor: 41.46).
11/1979; 281(5732):583-6. DOI: 10.1038/281583a0
The peripheral cytoplasm of macrophages is involved in the control of locomotion, secretion and endocytosis, events common to many eukaryotic cells. During these activities, the cortical cytoplasm, which contains numerous actin filaments1,2, appears to undergo reversible gel-sol transformations3: cycles of gelation and solation are demonstrable in suitably prepared macrophage extracts, and the gels contain tangled actin filaments4. These changes in consistency of cytoplasmic actin may regulate motile events in the macrophage periphery. Calcium in micromolar concentrations prevents gelation of crude macrophage cytoplasmic extracts4, providing a possible link to abundant indirect evidence implicating calcium in the regulation of locomotion, secretion and endocytosis5. Similar calcium-sensitive gelation phenomena occur in crude cell extracts from diverse cell types and may have a relevance for control of cell movements in general6-11. Actin gelation results from the cross-linking of actin filaments (F-actin) by other proteins. In macrophages, a high molecular weight actin-binding protein (ABP) is the principal actin cross-linking protein12. Cross-linking of actin by these purified actin-binding proteins, however, is insensitive to changes in the calcium concentration4,12, so that another factor must mediate the expression of a calcium effect. We have now isolated such a calcium-dependent regulatory protein from macrophages and call it gelsolin.
Available from: Michael O. Glocker
- "Depending on calcium ions gelsolin prevents further actin polymerization by covering the plus ends [49–53]. On the other hand it may encourage the formation of filaments by binding two monomers and therefore functions as a nucleus. "
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ABSTRACT: The treatment of Parkinson's disease by transplantation of dopaminergic (DA) neurons from human embryonic mesencephalic tissue is a promising approach. However, the origin of these cells causes major problems: availability and standardization of the graft. Therefore, the generation of unlimited numbers of DA neurons from various types of stem or progenitor cells has been brought into focus. A source for DA neurons might be conditionally immortalized progenitor cells. The temperature-sensitive immortalized cell line CSM14.1 derived from the mesencephalon of an embryonic rat has been used successfully for transplantation experiments. This cell line was analyzed by unbiased stereology of cell type specific marker proteins and 2D-gel electrophoresis followed by mass spectrometry to characterize the differentially expressed proteome. Undifferentiated CSM14.1 cells only expressed the stem cell marker nestin, whereas differentiated cells expressed GFAP or NeuN and tyrosine hydroxylase. An increase of the latter cells during differentiation could be shown. By using proteomics an explanation on the protein level was found for the observed changes in cell morphology during differentiation, when CSM14.1 cells possessed the morphology of multipolar neurons. The results obtained in this study confirm the suitability of CSM14.1 cells as an in vitro model for the study of neuronal and dopaminergic differentiation in rats.
01/2014; 2014(10):351821. DOI:10.1155/2014/351821
Available from: Sarah De Clercq
- "Gelsolin consists of 6 homologous structural domains, whereas CapG has only 3 such domains . They are both widely expressed in mammalian cells, including hematopoietic cells such as neutrophils and macrophages –. Gelsolin severs F-actin after which it remains attached to the barbed end of the filament as a cap, preventing further actin polymerization. CapG shares this capping function with gelsolin, but lacks its severing function , . "
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ABSTRACT: Podosomes are cellular structures acting as degradation 'hot-spots' in monocytic cells. They appear as dot-like structures at the ventral cell surface, enriched in F-actin and actin regulators, including gelsolin and L-plastin. Gelsolin is an ubiquitous severing and capping protein, whereas L-plastin is a leukocyte-specific actin bundling protein. The presence of the capping protein CapG in podosomes has not yet been investigated. We used an innovative approach to investigate the role of these proteins in macrophage podosomes by means of nanobodies or Camelid single domain antibodies. Nanobodies directed against distinct domains of gelsolin, L-plastin or CapG were stably expressed in macrophage-like THP-1 cells. CapG was not enriched in podosomes. Gelsolin nanobodies had no effect on podosome formation or function but proved very effective in tracing distinct gelsolin populations. One gelsolin nanobody specifically targets actin-bound gelsolin and was effectively enriched in podosomes. A gelsolin nanobody that blocks gelsolin-G-actin interaction was not enriched in podosomes demonstrating that the calcium-activated and actin-bound conformation of gelsolin is a constituent of podosomes. THP-1 cells expressing inhibitory L-plastin nanobodies were hampered in their ability to form stable podosomes. Nanobodies did not perturb Ser5 phosphorylation of L-plastin although phosphorylated L-plastin was highly enriched in podosomes. Furthermore, nanobody-induced inhibition of L-plastin function gave rise to an irregular and unstable actin turnover of podosomes, resulting in diminished degradation of the underlying matrix. Altogether these results indicate that L-plastin is indispensable for podosome formation and function in macrophages.
PLoS ONE 11/2013; 8(11):e78108. DOI:10.1371/journal.pone.0078108 · 3.23 Impact Factor
Available from: Michael P Schwartz
- "Filamin-A and gelsolin are actin-crosslinking and -severing proteins that could stabilize the dense F-actin bundles found within the WRAMP structure (Nakamura et al., 2011; Yin and Stossel, 1979). Talin-1 in the WRAMP structure might provide a means to anchor microfilaments to focal adhesions at the cortical plasma membrane. "
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ABSTRACT: Wnt5a directs the assembly of the Wnt-receptor-actin-myosin-polarity (WRAMP) structure, which integrates cell-adhesion receptors with F-actin and myosin to form a microfilament array associated with multivesicular bodies (MVBs). The WRAMP structure is polarized to the cell posterior, where it directs tail-end membrane retraction, driving forward translocation of the cell body. Here we define constituents of the WRAMP proteome, including regulators of microfilament and microtubule dynamics, protein interactions, and enzymatic activity. IQGAP1, a scaffold for F-actin nucleation and crosslinking, is necessary for WRAMP structure formation, potentially bridging microfilaments and MVBs. Vesicle coat proteins, including coatomer-I subunits, localize to and are required for the WRAMP structure. Electron microscopy and live imaging demonstrate movement of the ER to the WRAMP structure and plasma membrane, followed by elevation of intracellular Ca(2+). Thus, Wnt5a controls directional movement by recruiting cortical ER to mobilize a rear-directed, localized Ca(2+) signal, activating actomyosin contraction and adhesion disassembly for membrane retraction.
Developmental Cell 09/2013; 26(6):645-657. DOI:10.1016/j.devcel.2013.08.019 · 9.71 Impact Factor
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