Bianchi R, Garbuglia M, Verzini M, Giambanco I, Donato R
Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Italy.
Biochim Biophys Acta. 1994 Sep 29;1223(3):361-7. doi: 10.1016/0167-4889(94)90096-5.
Calpactin I, a heterotetrameric, cytoskeletal protein complex composed of two copies of annexin II cross-linked by two copies of p11, an S100-like protein, binds to the glial fibrillary acidic protein (GFAP) and cosediments with glial filaments (GF) in a Ca(2+)-dependent manner, apparently without affecting GFAP polymerization under the present experimental conditions. Cosedimentation of calpactin I with GF, which occurs at micromolar free Ca2+ concentrations, is proportional to the concentrations of both calpactin I and GFAP and does not occur under conditions where GFAP assembly is maximally inhibited by, e.g., S100 protein. Annexin II also cosediments with GF and binds to GFAP, although to much smaller extents. Other annexins, such as annexins I, V, and VI, or p11 do not bind to either GF or GFAP. Calpactin I and S100 protein bind to different sites on GFAP, as investigated by fluorescence spectroscopy using acrylodan-labeled GFAP. Calpactin I and S100 protein might act, in the presence of Ca2+, in a concerted manner to determine the number and topography of GF in differentiating and/or mature glial cells.
凝溶胶蛋白I是一种异源四聚体细胞骨架蛋白复合物，由两个膜联蛋白II拷贝和两个p11（一种S100样蛋白）拷贝交联而成，它以Ca(2+)依赖的方式与胶质纤维酸性蛋白（GFAP）结合，并与胶质丝（GF）共同沉降，在当前实验条件下显然不影响GFAP的聚合。凝溶胶蛋白I与GF的共同沉降发生在微摩尔游离Ca2+浓度下，与凝溶胶蛋白I和GFAP的浓度成正比，并且在GFAP组装被例如S100蛋白最大程度抑制的条件下不会发生。膜联蛋白II也与GF共同沉降并与GFAP结合，尽管程度要小得多。其他膜联蛋白，如膜联蛋白I、V和VI，或p11既不与GF也不与GFAP结合。通过使用丙烯罗丹标记的GFAP的荧光光谱研究发现，凝溶胶蛋白I和S100蛋白与GFAP上的不同位点结合。在Ca2+存在的情况下，凝溶胶蛋白I和S100蛋白可能协同作用，以确定分化和/或成熟胶质细胞中GF的数量和拓扑结构。
