Ca(2+)-dependent association of S100A6 (Calcyclin) with the plasma membrane and the nuclear envelope.
Expression of S100A6 (Calcyclin), a member of the S100 family and of Zn(2+)-binding proteins is elevated in a number of malignant tumors. In vitro the protein associates with several actin-binding proteins and annexins in a Ca(2+)-dependent manner. We have now studied the subcellular localization of S100A6 using a new, specific monoclonal antibody. Immunofluorescence microscopy of unfixed, ultrathin, frozen sections demonstrated a dual localization of S100A6 at the nuclear envelope and the plasma membrane of porcine smooth muscle only in the presence of Ca(2+). The same localization was found by immunofluorescence and immunogold electron microscopy as well as by confocal laser scanning microscopy with cultured, fixed, human CaKi-2 and porcine ST interphase cells. Upon cell division, however, S100A6 was found exclusively in the cytoplasm. Cell fractionation studies showed that S100A6 was present in the microsomal fraction in the presence of Ca(2+) and was released from this fraction by the addition of EGTA/EDTA but not by Triton X-100. The data demonstrate that S100A6 is localized both at the plasma membrane and the nuclear envelope in vivo and suggest a Ca(2+)-dependent interaction with annexins or other components of the nuclear envelope.
Stradal
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TB
Department of Cell Biology, Institute of Molecular Biology, Austrian Academy of Sciences, Billrothstrasse 11, A-5020 Salzburg, Austria.
Gimona
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D000818:Animals; D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D002118:Calcium / Q000494:pharmacology*; D002451:Cell Compartmentation; D018797:Cell Cycle Proteins; D002455:Cell Division; D002458:Cell Fractionation; D002462:Cell Membrane / Q000737:chemistry*; D005455:Fluorescent Antibody Technique; D006801:Humans; D008297:Male; D016253:Microscopy, Immunoelectron; D009130:Muscle, Smooth; D009685:Nuclear Envelope / Q000737:chemistry*; D011485:Protein Binding / Q000187:drug effects; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins / Q000276:immunology / Q000302:isolation & purification*; D013270:Stomach; D013552:Swine; D013737:Testis
D000911:Antibodies, Monoclonal; D018797:Cell Cycle Proteins; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins; C055351:S100A6 protein, human; D002118:Calcium