Two-stage autolysis of the catalytic subunit initiates activation of calpain I

Zimmerman, Un‐Jin P.; Schlaepfer, William W.

doi:10.1016/0167-4838(91)99009-h

Cited by 58 publications

(46 citation statements)

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“…Following activation of -calpain, the N-terminal 26 amino acids of calpain 1, and the N-terminal 91 amino acids, of CSS1, are removed via autolysis (72,44). It has been speculated that autolysis serves an important role in calpain function (2).…”

Section: Discussionmentioning

confidence: 99%

N Terminus of Calpain 1 Is a Mitochondrial Targeting Sequence

Badugu

Garcia

Bondada

et al. 2008

Journal of Biological Chemistry

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The ubiquitous m-and -calpains are thought to be localized in the cytosolic compartment, as is their endogenous inhibitor calpastatin. Previously, -calpain was found to be enriched in mitochondrial fractions isolated from rat cerebral cortex and SH-SY5Y neuroblastoma cells, but the submitochondrial localization of -calpain was not determined. In the present study, submitochondrial fractionation and digitonin permeabilization studies indicated that both calpain 1 and calpain small subunit 1, which together form -calpain, are present in the mitochondrial intermembrane space. The N terminus of calpain 1 contains an amphipathic ␣-helical domain, and is distinct from the N terminus of calpain 2. Calpain 1, but not calpain 2, was imported into mitochondria. Removal of the N-terminal 22 amino acids of calpain 1 blocked the mitochondrial calpain import, while addition of this N-terminal region to calpain 2 or green fluorescent protein enabled mitochondrial import. The N terminus of calpain 1 was not processed following mitochondrial import, but was removed by autolysis following calpain activation. Calpain small subunit 1 was not directly imported into mitochondria, but was imported in the presence of calpain 1. The presence of a mitochondrial targeting sequence in the N-terminal region of calpain 1 is consistent with the localization of -calpain to the mitochondrial intermembrane space and provides new insight into the possible functions of this cysteine protease.Calpains (EC 3.4.22.17) are a family of Ca 2ϩ -activated cysteine proteases, including both ubiquitous and tissue-specific isoforms, that cleave their substrate proteins at discrete sites to modulate activity (1-3). The best characterized, and the predominant calpains in the central nervous system, are the classical m-and -calpains. Their physiological roles have not been fully elucidated but include cell motility, cell differentiation, membrane fusion, platelet activation, and signal transduction (3). Also extensively investigated have been the pathological roles of calpains in cell death, where calpains can cleave key structural proteins and contribute to the release of death-related proteins such as apoptosis-inducing factor (AIF) 3 (4 -9). At present, it is unclear whether the -and m-calpains have distinct or overlapping functions. They are each heterodimers consisting of a unique 80-kDa large catalytic subunit (calpain 1 or 2) and a common 28-kDa small regulatory subunit (calpain small subunit 1 or 2) (2). In vitro, the substrates of m-and -calpains are similar, if not identical (10). Knock-out of the -calpain large subunit, calpain 1, results in viable mice with reduced platelet aggregation and impaired tyrosine phosphorylation in platelets, but not overt phenotype (11). Knock-out of the m-calpain large subunit, calpain 2, or of calpain small subunit 1 (CSS1) is embryonically lethal (12)(13)(14).Both m-and -calpains are considered to be cytosolic enzymes (2,3, 15,16). An association of m-and -calpains with subcellular organelles including endoplasmic ret...

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Section: Discussionmentioning

confidence: 99%

N Terminus of Calpain 1 Is a Mitochondrial Targeting Sequence

Badugu

Garcia

Bondada

et al. 2008

Journal of Biological Chemistry

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“…Identification of two steps in the autolysis of the mcalpain large subunit makes the process more analogous to that seen with p-calpain. Zimmerman and Schlaepfer [8] identified two cleavage sites in pu-calpain as shown in Table I. However in contrast to m-calpain, Zimmerman and Schlaepfer reported that the change in Ca*+ sensitivity of p-calpain occurred after the second cleavage in the large subunit.…”

Section: Discussionmentioning

confidence: 99%

“…[3,. Autolysis of the large subunit ofp-calpain initially involves degradation at the N-terminus and formation of polypeptides of approximately 78 kDa and 76 kDa [8,9] or only 76 kDa [5]. These polypeptides can readily be resolved from the 80 kDa polypeptide on SDS-polyacrylamide gel electrophoresis.…”

Section: Introductionmentioning

confidence: 99%

Structural modifications associated with the change in Ca²⁺ sensitivity on activation of m‐calpain

Brown

Crawford

1993

FEBS Letters

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“…The 28-kDa subunit of m-calpain is autolyzed more rapidly than the 80-kDa subunit (45,73), whereas autolysis of the 80-kDa subunit in the -calpain molecule seems to proceed as rapidly as or even more rapidly than autolysis of the 28-kDa subunit in this molecule (45,68,504).…”

Section: Autolysis and The Proenzyme Questionmentioning

confidence: 98%

The Calpain System

Goll

Thompson

et al. 2003

Physiological Reviews

2,571

2,801

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Goll, Darrel E., Valery F. Thompson, Hongqi Li, Wei Wei, and Jinyang Cong. The Calpain System. Physiol Rev 83: 731–801, 2003; 10.1152/physrev.00029.2002.—The calpain system originally comprised three molecules: two Ca2+-dependent proteases, μ-calpain and m-calpain, and a third polypeptide, calpastatin, whose only known function is to inhibit the two calpains. Both μ- and m-calpain are heterodimers containing an identical 28-kDa subunit and an 80-kDa subunit that shares 55–65% sequence homology between the two proteases. The crystallographic structure of m-calpain reveals six “domains” in the 80-kDa subunit: 1) a 19-amino acid NH2-terminal sequence; 2) and 3) two domains that constitute the active site, IIa and IIb; 4) domain III; 5) an 18-amino acid extended sequence linking domain III to domain IV; and 6) domain IV, which resembles the penta EF-hand family of polypeptides. The single calpastatin gene can produce eight or more calpastatin polypeptides ranging from 17 to 85 kDa by use of different promoters and alternative splicing events. The physiological significance of these different calpastatins is unclear, although all bind to three different places on the calpain molecule; binding to at least two of the sites is Ca2+ dependent. Since 1989, cDNA cloning has identified 12 additional mRNAs in mammals that encode polypeptides homologous to domains IIa and IIb of the 80-kDa subunit of μ- and m-calpain, and calpain-like mRNAs have been identified in other organisms. The molecules encoded by these mRNAs have not been isolated, so little is known about their properties. How calpain activity is regulated in cells is still unclear, but the calpains ostensibly participate in a variety of cellular processes including remodeling of cytoskeletal/membrane attachments, different signal transduction pathways, and apoptosis. Deregulated calpain activity following loss of Ca2+ homeostasis results in tissue damage in response to events such as myocardial infarcts, stroke, and brain trauma.

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Two-stage autolysis of the catalytic subunit initiates activation of calpain I

Cited by 58 publications

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N Terminus of Calpain 1 Is a Mitochondrial Targeting Sequence

N Terminus of Calpain 1 Is a Mitochondrial Targeting Sequence

Structural modifications associated with the change in Ca²⁺ sensitivity on activation of m‐calpain

The Calpain System

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Two-stage autolysis of the catalytic subunit initiates activation of calpain I

Cited by 58 publications

References 0 publications

N Terminus of Calpain 1 Is a Mitochondrial Targeting Sequence

N Terminus of Calpain 1 Is a Mitochondrial Targeting Sequence

Structural modifications associated with the change in Ca2+ sensitivity on activation of m‐calpain

The Calpain System

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Structural modifications associated with the change in Ca²⁺ sensitivity on activation of m‐calpain