Abdul Khaleque Md, Terada Kazutoyo, Gotoh Tomomi, Hafizur Rahman Md, Mori Masataka
Department of Molecular Genetics, Kumamoto University School of Medicine, Japan.
Cell Stress Chaperones. 2002 Apr;7(2):156-66. doi: 10.1379/1466-1268(2002)007<0156:cafaoa>2.0.co;2.
DnaJ homologs are cochaperones of the heat shock protein 70 (hsp70) family. Homologs dj1 (hsp40/hdj-1/ DjB1), dj2 (HSDJ/hdj-2/rdj-1/DjA1), and dj3 (cpr3/DNAJ3/HIRIP4/rdj2/DjA2) have been identified in the mammalian cytosol and characterized. In this paper we characterized newly found dj4 (DjA4) and compared it with other chaperones. The dj4 messenger ribonucleic acid (mRNA) and protein were expressed strongly in heart and testis, moderately in brain and ovary, and weakly in other tissues in mice. Dj4 constituted about 1% of the total protein in heart. Testis gave extraspecies of dj4 mRNA and protein in addition to those seen in other tissues. On subcellular fractionation of the mouse heart, dj4 was recovered mostly in the cytosol fraction. In immunocytochemical analysis of the H9c2 heart muscle cells, dj4 and heat shock cognate 70 (hsc70) colocalized in the cytoplasm under normal conditions, whereas they colocalized in the nucleus after heat shock. When H9c2 cells were differentiated by culturing for up to 28 days with a lowered serum concentration, dj4 was increased markedly, dj3 was increased moderately, and dj1 and dj2 were little changed. The homolog dj4 as well as hsp70, dj1, and dj2 were induced in H9c2 cells by heat treatment at 43 degrees C for 30 minutes, whereas hsc70 and dj3 were not induced. Heat pretreatment promoted survival of cells after severe heat shock at 47 degrees C for 90 minutes or 120 minutes. H9c2 cells overexpressing hsp70 were more resistant to severe heat shock, and a better survival was obtained when dj4 or dj2 was co-overexpressed with hsp70. Taking a high concentration of dj4 in heart into consideration, these results suggest that the hsc70/hsp70-dj4 chaperone pair protects the heart muscle cells from various stresses.
DnaJ同源物是热休克蛋白70（hsp70）家族的共伴侣蛋白。在哺乳动物细胞质中已鉴定出同源物dj1（hsp40/hdj-1/DjB1）、dj2（HSDJ/hdj-2/rdj-1/DjA1）和dj3（cpr3/DNAJ3/HIRIP4/rdj2/DjA2）并对其进行了表征。在本文中，我们对新发现的dj4（DjA4）进行了表征，并将其与其他伴侣蛋白进行了比较。dj4信使核糖核酸（mRNA）和蛋白质在小鼠心脏和睾丸中强烈表达，在脑和卵巢中中度表达，在其他组织中弱表达。Dj4约占心脏总蛋白的1%。除了在其他组织中可见的那些之外，睾丸还产生了dj4 mRNA和蛋白质的额外物种。对小鼠心脏进行亚细胞分级分离时，dj4大多在细胞质分级分离物中回收。在对H9c2心肌细胞进行免疫细胞化学分析时，在正常条件下，dj4和热休克同源蛋白70（hsc70）在细胞质中共定位，而在热休克后它们在细胞核中共定位。当H9c2细胞在低血清浓度下培养长达28天进行分化时，dj4显著增加，dj3适度增加，而dj1和dj2变化不大。同源物dj4以及hsp70、dj1和dj2在H9c2细胞中通过在43℃热处理30分钟而被诱导，而hsc70和dj3未被诱导。热预处理促进了细胞在47℃严重热休克90分钟或120分钟后的存活。过表达hsp70的H9c2细胞对严重热休克更具抗性，当dj4或dj2与hsp70共过表达时，获得了更好的存活率。考虑到心脏中dj4的高浓度，这些结果表明hsc70/hsp70-dj4伴侣蛋白对可保护心肌细胞免受各种应激。
