Laboratory of Cell Biochemistry, Department of Biological Science, Graduate School of Science and Engineering, Iwate University, Morioka, Japan.
Technical Support Center for Life Science Research, Iwate Medical University, Morioka, Japan.
Biochem Biophys Res Commun. 2022 Jun 18;609:149-155. doi: 10.1016/j.bbrc.2022.04.002. Epub 2022 Apr 4.
Calpains are Ca-dependent cysteine proteases involved in various intercellular physiological functions. Although most calpains exist in the cytosol, four isoforms of calpain (calpains-1, -2, -5, -10) are also localized in the mitochondria. In the present study, we examined the mitochondrial localization of calpain-13, as a novel mitochondrial calpain, in C57BL/6J mice. The tissue distribution and mitochondrial subfractionation of calpain-13 were investigated using western blotting. Calpain-13 was present in both the mitochondrial membrane (outer membrane and inner membrane) and soluble (intermembrane space and matrix) fractions. Through immunohistochemistry, calpain-13 was found to be expressed in the cerebral cortex and hippocampus of the mouse brain. We further confirmed the localization of calpain-13 in the mitochondria of the mouse brain using immunoelectron microscopy. Our present study thus revealed that calpain-13 is localized in the mitochondria, in addition to the cytosol, in the mouse brain. Future studies investigating the enzymatic properties and physiological functions of both cytosolic and mitochondrial calpain-13 will shed light on the potential involvement of calpain-13 in neurodegenerative diseases including Parkinson's disease and Alzheimer's disease.
钙蛋白酶是依赖 Ca2+的半胱氨酸蛋白酶，参与多种细胞间的生理功能。虽然大多数钙蛋白酶存在于细胞质中，但钙蛋白酶的四个同工型（钙蛋白酶-1、-2、-5、-10）也定位于线粒体中。在本研究中，我们在 C57BL/6J 小鼠中研究了新型线粒体钙蛋白酶-13 的线粒体定位。使用 Western blot 法研究了钙蛋白酶-13 的组织分布和线粒体亚部分。钙蛋白酶-13 存在于线粒体膜（外膜和内膜）和可溶性部分（膜间空间和基质）中。通过免疫组织化学，我们发现钙蛋白酶-13 在小鼠大脑的大脑皮层和海马体中表达。我们进一步通过免疫电镜确认了钙蛋白酶-13 在小鼠大脑线粒体中的定位。因此，我们的研究表明，钙蛋白酶-13 除存在于细胞质中外，还定位于小鼠大脑的线粒体中。未来研究钙蛋白酶-13 的胞质和线粒体的酶学特性和生理功能将揭示钙蛋白酶-13 可能参与包括帕金森病和阿尔茨海默病在内的神经退行性疾病。
