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

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 Ca2+ 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.

Immune system aging and the aging-related diseases in the COVID-19 era

“…Our further, as yet unpublished data indicate that this reduction in calpain amounts and activities is common also for other peripheral immune cells, including monocytes and NK cells. On the other hand we have shown that inhibition of calpains in the resting T cells leads to their decreased proliferation, cytokine secretion, and activation in relation to changed levels of activation of some molecules important for T cell signal transduction, including phospholipase C gamma, p56Lck, NFκB, and ZAP-70, all of which were earlier demonstrated to be affected by aging [ 88 , 89 ].…”

Dysregulation of Calpain Proteolytic Systems Underlies Degenerative Vascular Disorders

“…Conventional calpains are localized to the majority of vascular systems, including veins 15 ) , arteries 16 ) and capillaries 17 ) , and are also expressed in ECs 16 , 18 ) , vascular smooth muscle cells (VSMCs) 19 ) and adventitial fibroblasts 20 ) . In addition to the vascular component cells, calpains are localized to immune cells 21 , 22 ) , which can be recruited into blood vessels in response to inflammatory insults. In addition to the conventional calpain isozymes, calpastatin, an endogenous calpain inhibitor, colocalizes with the proteases, and negatively regulates their proteolytic activity 12 – 14 ) .…”

Photoreceptor Cell Calcium Dysregulation and Calpain Activation Promote Pathogenic Photoreceptor Oxidative Stress and Inflammation in Prodromal Diabetic Retinopathy

“…Cal-pain1 (m-calpain) and calpain-2 (m-calpain) are the best characterized and most ubiquitously expressed calpains, and are activated by micromolar and millimolar calcium concentrations, respectively. Calpains belong to a family of calcium-dependent cysteine proteases with at least 16 members and are widely distributed in cells, including immune cells 61 and vascular cells. 62 They can be detected in multiple subcellular organelles, including mitochondria.…”