Huang L, Mivechi N F, Moskophidis D
Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15th St., Augusta, GA 30912-3175, USA.
Mol Cell Biol. 2001 Dec;21(24):8575-91. doi: 10.1128/MCB.21.24.8575-8591.2001.
The murine hsp70 gene family includes the evolutionarily conserved hsp70.1 and hsp70.3 genes, which are the major proteins induced by heat and other stress stimuli. hsp70.1 and hsp70.3 encode identical proteins which protect cells and facilitate their recovery from stress-induced damage. While the hsp70 gene family has been widely studied and the roles of the proteins it encodes as molecular chaperones in a range of human pathologies are appreciated, little is known about the developmental regulation of hsp70.1 and hsp70.3 expression and the in vivo biological function of their products. To directly study the physiological role of these proteins in vivo, we have generated mice deficient in heat shock protein 70 (hsp70) by replacing the hsp70.1 or hsp70.3 gene with an in-frame beta-galactosidase sequence. We report here that the expression of hsp70.1 and hsp70.3 is developmentally regulated at the transcriptional level, and an overlapping expression pattern for both genes is observed during embryo development and in the tissues of adult mice. hsp70.1-/- or hsp70.3-/- mice are viable and fertile, with no obvious morphological abnormalities. In late embryonic stage and adult mice, both genes are expressed constitutively in tissues exposed directly to the environment (the epidermis and cornea) and in certain internal organs (the epithelium of the tongue, esophagus, and forestomach, and the kidney, bladder, and hippocampus). Exposure of mice to thermal stress results in the rapid induction and expression of hsp70, especially in organs not constitutively expressing hsp70 (the liver, pancreas, heart, lung, adrenal cortex, and intestine). Despite functional compensation in the single-gene-deficient mice by the intact homologous gene (i.e., hsp70.3 in hsp70.1-/- mice and vice versa), a marked reduction in hsp70 protein expression was observed in tissues under both normal and heat stress conditions. At the cellular level, inactivation of hsp70.1 or hsp70.3 resulted in deficient maintenance of acquired thermotolerance and increased sensitivity to heat stress-induced apoptosis. The additive or synergistic effects exhibited by coexpression of both hsp70 genes, and the evolutionary significance of the presence of both hsp70 genes, is hence underlined.
小鼠热休克蛋白70（hsp70）基因家族包括进化上保守的hsp70.1和hsp70.3基因，它们是由热和其他应激刺激诱导产生的主要蛋白质。hsp70.1和hsp70.3编码相同的蛋白质，这些蛋白质可保护细胞并促进其从应激诱导的损伤中恢复。虽然hsp70基因家族已得到广泛研究，并且其编码的蛋白质作为分子伴侣在一系列人类疾病中的作用也已为人所知，但对于hsp70.1和hsp70.3表达的发育调控及其产物的体内生物学功能却知之甚少。为了直接研究这些蛋白质在体内的生理作用，我们通过用框内β-半乳糖苷酶序列取代hsp70.1或hsp70.3基因，构建了热休克蛋白70（hsp70）缺陷型小鼠。我们在此报告，hsp70.1和hsp70.3的表达在转录水平受到发育调控，并且在胚胎发育过程和成年小鼠组织中观察到这两个基因的重叠表达模式。hsp70.1-/-或hsp70.3-/-小鼠可存活且可育，无明显形态异常。在胚胎后期和成年小鼠中，这两个基因在直接暴露于环境的组织（表皮和角膜）以及某些内部器官（舌、食管和前胃的上皮，以及肾脏、膀胱和海马体）中组成性表达。将小鼠暴露于热应激会导致hsp70迅速诱导和表达，尤其是在非组成性表达hsp70的器官（肝脏、胰腺、心脏、肺、肾上腺皮质和肠道）中。尽管单基因缺陷小鼠中的完整同源基因可进行功能补偿（即hsp70.1-/-小鼠中的hsp70.3，反之亦然），但在正常和热应激条件下的组织中均观察到hsp70蛋白表达明显降低。在细胞水平上，hsp70.1或hsp70.3的失活导致获得性耐热性维持不足，并增加了对热应激诱导的细胞凋亡的敏感性。因此，强调了两个hsp70基因共表达所表现出的累加或协同效应，以及两个hsp70基因存在的进化意义。
