MSJ-1, a mouse testis-specific DnaJ protein, is highly expressed in haploid male germ cells and interacts with the testis-specific heat shock protein Hsp70-2.
The MSJ-1 gene encodes a murine DnaJ homologue that is expressed specifically in adult testis. DnaJ proteins act as cochaperones of Hsp70 proteins in promoting diverse cellular functions. In this study we used recombinant MSJ-1 proteins to produce MSJ-1 antiserum and to carry out in vitro binding assays. In a wide immunoscreening of mouse tissues, affinity-purified MSJ-1 antibodies recognize a unique protein of 30 kDa in male germ cells only. MSJ-1 is able to interact with the testis-specific Hsp70-2 protein and can be coimmunoprecipitated with Hsp70-2 from spermatogenic cells; binding of these two chaperones is consistent with the presence of a third component, which is so far unknown. MSJ-1 is weakly detected in early round spermatids, and its protein content increases in cytodifferentiating spermatids where it colocalizes with the developing acrosome and their postnuclear region. Hsp70-2, which is known to be highly expressed in meiotic cells, shows a subcellular localization in late differentiating spermatids that overlaps that of MSJ-1. MSJ-1 is also maintained in testicular and epididymal spermatozoa, where it sharply demarcates into two distinct cell areas; the outer surface of the acrosomal vesicle, and the centrosomal area. On the whole, our findings are consistent with a role for MSJ-1 in acrosome formation and centrosome adjustment during spermatid development, whereas its presence in mature spermatozoa suggests a special function during fertilization, shortly afterward, or both.
Berruti
G
G
Department of Biology, University of Milano, 20133 Milano, Italy. giovanni.berruti@unimi.it
Martegani
E
E
D000375:Aging; D000818:Animals; D005455:Fluorescent Antibody Technique; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000032:analysis / Q000378:metabolism*; D006238:Haploidy; D006360:Heat-Shock Proteins / Q000032:analysis* / Q000378:metabolism; D015151:Immunoblotting; D007150:Immunohistochemistry; D007163:Immunosorbent Techniques; D008297:Male; D008540:Meiosis; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D013087:Spermatids / Q000737:chemistry; D013094:Spermatozoa / Q000737:chemistry*; D013737:Testis / Q000737:chemistry* / Q000254:growth & development
C494642:Dnajb3 protein, mouse; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins