Abstract
Calpain is a conserved family of calcium-dependent, cytosolic, neutral cysteine proteases. The best characterized members of the family are the ubiquitously expressed calpain 1 and calpain 2. They perform controlled proteolysis of their target proteins. The regulation of these enzymes includes autolysis, calcium, phosphorylation as a posttranslational modification, and binding of calpastatin, phospholipids or activator proteins, respectively. Calpain are implicated in many physiological and pathological processes. They have significant role in the cell proliferation, differentiation and migration in a variety of mammalian cell types, contributing to the development of angiogenesis, vascular remodeling, and cancer. Therefore the knowledge of the precise mechanism of calpain signaling could provide therapeutic approaches in these processes.
Highlights
Calpain was first described as a neutral, calcium-activated proteinase in the soluble fraction of rat brain [1]
Calpain 2 can be directly phosphorylated at Ser50 by the extracellular signal-regulated protein kinase (ERK) after epidermal growth factor (EGF) stimulation causing the activation of the enzyme independently of calcium [52,53]
More importantly we found that conditional knockout of calpain 4 and calpain inhibitor MDL28170 prevent the progression of pulmonary vascular remodeling induced by hypoxia and monocrotaline [92]
Summary
Calpain was first described as a neutral, calcium-activated proteinase in the soluble fraction of rat brain [1]. It accomplishes its proteolytic activity in the cytoplasm, not in the lysosomes at a neutral pH. There are 15 genes encoding the large catalytic subunits, and two genes encoding small regulatory subunits (Table 1) [4,5]. They can be classified according to their localization (ubiquitous or tissue-specific).
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