beta-Internexin, a ubiquitous intermediate filament-associated protein.
In this article we show a Triton-insoluble, intermediate filament-associated protein of approximately 70 kD to be expressed ubiquitously in diverse mammalian cell types. This protein, assigned the name beta-internexin, exhibits extreme homology in each of the various cell lines as demonstrated by identical limited peptide maps, similar mobilities on two-dimensional gels, and detection in Triton-soluble and -insoluble extracts. beta-Internexin also shares some degree of homology with alpha-internexin, an intermediate filament-associated protein isolated and purified from rat spinal cord, which accounts for the immunologic cross-reactivity displayed by these polypeptides. Light microscopic immunolocalization of beta-internexin with a monoclonal antibody (mAb-IN30) reveals it to be closely associated with the vimentin network in fibroblasts. The antigen is also observed to collapse with the vimentin reticulum during the formation of a juxtanuclear cap induced by colchicine treatment. Ultrastructural localization, using colloidal gold, substantiates the affinity of beta-internexin for cytoplasmic filaments and, in addition, demonstrates its apparent exclusion from the intranuclear filament network. We examine also the resemblance of beta-internexin to a microtubule-associated polypeptide and the constitutively synthesized mammalian heat shock protein (HSP 68/70).
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D003599:Cytoskeleton / Q000032:analysis; D005260:Female; D005347:Fibroblasts / Q000032:analysis*; D005455:Fluorescent Antibody Technique; D005910:Glioma / Q000032:analysis*; D050883:HSC70 Heat-Shock Proteins; D006801:Humans; D006822:Hybrid Cells / Q000032:analysis*; D007382:Intermediate Filaments / Q000378:metabolism; D007614:Macropodidae; D008297:Male; D009447:Neuroblastoma / Q000032:analysis*; D010455:Peptides / Q000032:analysis; D010802:Phylogeny; D011506:Proteins / Q000276:immunology / Q000302:isolation & purification* / Q000378:metabolism; D013045:Species Specificity
D000911:Antibodies, Monoclonal; D050883:HSC70 Heat-Shock Proteins; C494371:HSPA8 protein, human; C494373:Hspa8 protein, rat; D010455:Peptides; D011506:Proteins