Bioscience Reports (2020) 40 BSR20200552 https://doi.org/10.1042/BSR20200552 Research Article Calpain-2 participates in the process of calpain-1 inactivation Fumiko Shinkai-Ouchi1, Mayumi Shindo2, Naoko Doi1, Shoji Hata1 and Yasuko Ono1 1Calpain Project, Department of Basic Medical Sciences, Tokyo Metropolitan Institute of Medical Science (TMiMS), 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156- 8506, Japan; 2Center for Basic Technology Research, Tokyo Metropolitan Institute of Medical Science (TMiMS), 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156- 8506, Japan Downloaded from http://portlandpress.com/bioscirep/article-pdf/40/11/BSR20200552/896871/bsr-2020-0552.pdf by guest on 28 September 2021 Correspondence: Yasuko Ono (
[email protected]) Calpain-1 and calpain-2 are highly structurally similar isoforms of calpain. The calpains, a family of intracellular cysteine proteases, cleave their substrates at specific sites, thus modifying their properties such as function or activity. These isoforms have long been considered to function in a redundant or complementary manner, as they are both ubiq- uitously expressed and activated in a Ca2+- dependent manner. However, studies using isoform-specific knockout and knockdown strategies revealed that each calpain species carries out specific functions in vivo. To understand the mechanisms that differentiate calpain-1 and calpain-2, we focused on the efficiency and longevity of each calpain species after activation. Using an in vitro proteolysis assay of troponin T in combination with mass spectrometry, we revealed distinctive aspects of each isoform. Proteolysis mediated by calpain-1 was more sustained, lasting as long as several hours, whereas proteolysis me- diated by calpain-2 was quickly blunted.