[摘要]：In human red blood cells, protein 4.1 (4.1R) is an 80-kDa polypeptide that stabilizes the spectrin-actin network and anchors it to the plasma membrane. In non-erythroid cells there is a great variety of 4.1R isoforms, mainly generated by alternative pre-mRNA splicing, which localize at various intracellular sites, including the nucleus. We studied protein 4.1R distribution in relation to beta-spectrin, actin and cytokeratin during Xenopus oogenesis. Immunoprecipitation experiments indicate that at least two isoforms of protein 4.1R are present in Xenopus laevis oocytes: a 56-kDa isoforms of protein 4.1R associate with the 100-kDa isoform of beta-spectrin. Moreover, the 56-kDa from protein 4.1R distribution is in the peripheral cytoplasm, in the mitochondrial cloud (MC) and in the GV of previtellogenic oocytes. In the cytoplasm of vitellogenic occytes, a loose network of fibers stained by the anti-protein 4.1R antibody spreads across the cytoplasm. beta-spectrin has a similar distribution. Protein 4.1R was found to colocalize with actin in the cortex of oocytes in the form of fluorescent dots. Double immunolocalization of protein 4.1R and cytokeratin depicts two seperate networks that overlap throughout the whole cytoplasm. Protein 4.1R filaments partially colocalize with cytokeratin in both the animal and vegetal hemispheres. We hypothesize that protein 4.1R could function as a linker protein between cytokeratin and the actin-based cytoskeleton. (C) 2009 Elsevier GmbH. All rights reserved.
