Calpain activation

Calpain inhibition may represent an important mechanism for future drug development. Control of calpain activity may limit the invasive properties of cells and thereby provides a possible mechanism to limit the invasiveness of tumors or inhibits the development of chronic inflammation. For the moment, pharmacological inhibitors of calpains are still not capable of differentiating among different calpain isoforms in cellular systems or in vivo. The importance of calpains in diseases will continue to stimulate the development of new and better inhibitors. 

Myocardial infarcts Ca2+ homeostasis is lost in ischemic areas, triggering inappropriate calpain activity. Desmin and a-spectrin are degraded in ischemic hearts by synthetic calpain inhibitors. Protein and mRNA levels of m and (./-calpain increase after myocardial infarction40-43... 

Obsessive-compulsive disorders Erythrocytes from patients with obsessive-compulsive disorder have significantly higher calpain activities than normal controls which could not be attributed to differences in memory function46... 

Becker s muscular dystrophies deficiency of dystrophin, a membrane-associated protein, resulting in an increased Ca2+ level in muscle, loss of Ca2+ homeostasis, and inappropriate calpain activity. Spencer, 2000... 

REGULATION OF CALPAIN ACTIVITY. THE CALCIUM REQUIREMENT PROBLEM... 

Calpastatin was identified in experiments in which no calpain activity could be observed in crude skeletal muscle homogenates. After precipitation of calpain at pH 6.5 (Dayton et al., 1976), the supernatant was found to contain a heat-resistant factor with calpain inhibitory activity (Okitani et al., 1976), which was later named calpastatin. Early attempts to characterize and purify the factor were unsuccessful, due to the susceptibility of the protein to proteolytic degradation. 

Mathews, P.M., Jiang, Y., Schmidt, S.D., Grbovic, O.M., Mercken, M., Nixon, R.A., 2002, Calpain activity regulates the cell surface distribution of amyloid precursor protein. Inhibition of calpains enhances endosomal generation ofB-cleaved C-terminal APP fragments., J. Biol. Chem., 277, 36415— 36424... 

McClelland, P., Lash, J., Hataway, D., 1989, Identification of major autolytic cleavage sites in the regulatory subunit of vascular Calpain II. A comparison of partial amino-terminal sequences to deduced sequence from complementary DNA, J. Biol. Chem., 264, 17428—17431 Mellgren, R., Song, K., Mericle, M., 1993, m-Calpain requires DNA for activity on nuclear proteins at low calcium concentrations, J. Biol. Chem., 268, 653—657 Melloni, E., Michetti, M., Salamino, F., Pontremoli, S., 1998, Molecular and functional properties of a calpain activator protein specific for [L-isoforms, J. Biol. Chem., 273, 12827—12831 Moldoveanu, T., Hosfield, C., Lim, D., Elce, J., Jia, Z., Davies, P., 2002, A Calcium switch aligns the active site of calpain, Cell, 108, 649—660... 

Chen, M., and Fernandez, H. L. (2004). Stimulation of beta-amyloid precursor protein alpha-processing by phorbol ester involves calcium and calpain activation. Biochem Biophys Res Commun 316, 332-340. 

Wang, K.K.W., Nath, R., Raser, K.J., and Hajimohammadreza, I. 1996. Maitotoxin induces calpain activation in SH-SY5Y neuroblastoma cells and cerebrocortical cultures. Archives of Biochemistry and Biophysics 331, 208-214. 

Gafni J, Ellerby LM (2002) Calpain activation in Huntington s disease. J Neurosci 22 4842 849. 

Peltier J, Bellocq A, Perez J,DoublierS, Dubois YC, Haymann JP,CamusslG,and Baud L.Calpain activation and secretion promote glomerular injury in experimental glomerulonephritis evidence from calpastatin-transgenic mice. J Am Soc Nephrol 17 3415-3423, 2006. 

A previous report has implicated a role of calpain in mediating the tissue injury caused by the chemical threat agent sulfur mustard. Specifically, tissue homogenates from mouse ear skin exposed to sulfur mustard displayed a marked increase in calpain activity (170% increase 24 h after treatment Powers et al. 2000). These findings underscore the need to identify effective antiproteases with therapeutic use in reducing, or eliminating, tissue injuries. Since excitotoxicity is related directly to calpain activation, it can be surmised that sulfur mustard exposures may be linked to excitotoxicity. 

McCollum, A.T., Nasr, P., and Estus, S., 2002. Calpain activates caspase-3 during UV-induced neuronal death but only calpain is necessary for death, J. Neurochem., 82, pp. 1208-1220. 

Calpains are cytosolic Ca- -dependent cysteine proteases [45]. They are located close to the cytoskeleton and mostly degrade cytoskeletal proteins, protein kinases, phosphatases, membrane receptors, transport proteins, and regulatory proteins [46,47]. Stimulation of calpain activity was shown following oxidative stress [48-55] in combination with an increase in intracellular Ca concentration [50, 54]. No studies exist that point towards a selective recognition of oxidized protein substrates by calpains [56]. However, it has been demonstrated that the oxidized cytoskeletal protein ezrin is degraded by the proteasome [57]. 

Renal ischemia/ reperfusion injiuy in vivo activates caspase-1 and caspase-3 [58,67]. In a murine model of ischemia/reperfusion injury, ZVAD-fmk, a pancaspase inhibitor, was shown to attenuate reperfusion-induced DNA damage (as determined by TUNEL assay) and inflammation [67]. Recent studies by Edelstein et al. [62, 62a] help establish a link between the inflammatory aspects of the ischemic/reperfusion injury and caspase activation. In these studies it was observed that caspase 1 deficient mice were protected from ischemia-reperfusion injury. Aware that IL-18 is expressed after several cell stresses and is activated by caspase-1, the authors observed that IL-18 expression is increased in ischemia-reperfusion and caspase-1 converts IL-18 precursor to its active form. Furthermore in caspase-defi-cient mice the activity of IL-18 does not increase and the use of a neutralizing antibody to IL-18 offers protection in wild-type animals. The authors also demonstrate reduced leukocyte infiltration in caspase-1 deficient mice, completing a loop between cell injury, initiation of inflammation, and caspase-1 activation. Another study has demonstrated that caspase-3 activation during ischemia/reperfusion injury may be involved in the downregulation of calpastatin, an inhibitor of calpain [68] indicating a role of caspases for calpain activation during renal injury. 

Two enzymatic systems, i.e., calpain and cathepsin influence tenderization of meat. The activity of calpain reduces under high pressure. The activity of p-calpain is also reduced during ageing (Ouali, 1990). Qin et al. (2001) showed that high-pressure treatment (100-300 MPa, 10 min) of beef resulted in a decrease in the total calpain activity however, the acid phosphatase and alkaline phosphatase activities were not significantly reduced. Homma et al. (1995) found that the total activity of calpain in pressurized muscle increased due to a reduction in the level of calpastatin because of its pressure sensitivity this in turn resulted in meat tenderization. 

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