Roles of calpain-calpastatin system (CCS) in human T cell activation.

// Anna Mikosik 1 , Aleksandra Jasiulewicz 1 , Agnieszka Daca 2 , Izabella Henc 2 , Joanna E. Frąckowiak 1 , Katarzyna Ruckemann-Dziurdzinska 2 , Jerzy Foerster 3 , Aurelie Le Page 4 , Ewa Bryl 2 , Tamas Fulop 4 and Jacek M. Witkowski 1 1 Department of Pathophysiology, Medical University of Gdansk, Gdansk, Poland 2 Department of Pathology and Experimental Rheumatology, Medical University of Gdansk, Gdansk, Poland 3 Department of Clinical and Social Gerontology, Medical University of Gdansk, Gdansk, Poland 4 Research Center on Ageing, University of Sherbrooke, Sherbrooke, Quebec, Canada Correspondence to: Jacek M. Witkowski, email: // Keywords : T cells, calpain, calpastatin, proliferation, cytokines, Immunology and Microbiology Section, Immune response, Immunity Received : August 25, 2016 Accepted : November 02, 2016 Published : November 09, 2016 Abstract The immune response is determined by the speed of the T cell reaction to antigens assured by a state of readiness for proliferation and cytokine secretion. Proliferation, apoptosis and motion of many cell types are controlled by cytoplasmic proteases - µ- and m-calpain - and their inhibitor calpastatin, together forming the “calpain-calpastatin system” (CCS), assumed to modify their targets only upon activation-dependent cytoplasmic Ca 2+ increase. Contrastingly to this notion, using quantitative real time PCR and semiquantitative flow cytometry respectively, we show here that the CCS genes are constitutively expressed, and that both calpains are constitutively active in resting, circulating human CD4 + and CD8 + lymphocytes. Furthermore, we demonstrate that calpain inhibition in the resting T cells prevents them from proliferation in vitro and greatly reduces secretion of multiple cytokines. The mechanistic reason for these effects of calpain inhibition on T cell functions might be the demonstrated significant reduction of the expression of active (phosphorylated) upstream signalling molecules, including the phospholipase C gamma, p56Lck and NFκB, in the inhibitor-treated cells. Thus, we propose that the constitutive, self-regulatory calpain-calpastatin system activity in resting human T cells is a necessary, controlling element of their readiness for complex and effective response to antigenic challenge.