Calpain (Ca(2+)-dependent thiol protease) in erythrocytes of young and old individuals.

Glaser, Tova; Schwarz-Benmeir, N; Barnoy, Sivia; Barak, Shimon; Eshhar, Zelig; Kosower, Nechama S.

doi:10.1073/pnas.91.17.7879

Cited by 57 publications

(39 citation statements)

References 34 publications

(45 reference statements)

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“…54,55 Furthermore, in erythrocytes of aged and hypertensive individuals the calpain inhibitor calpastatin is partially degraded and diminished resulting in increased calpain activity. 56,57 Interestingly, there are several potential crosstalks between calpain and caspases. Both types of proteases do not only have several common substrates but may also modulate each other's activity.…”

Section: Discussionmentioning

confidence: 99%

Human mature red blood cells express caspase-3 and caspase-8, but are devoid of mitochondrial regulators of apoptosis

et al. 2001

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Although proteases of the caspase family are essential mediators of apoptosis in nucleated cells, in anucleate cells their presence and potential functions are almost completely unknown. Human erythrocytes are a major cell population that does not contain a cell nucleus or other organelles. However, during senescence they undergo certain morphological alterations resembling apoptosis. In the present study, we found that mature erythrocytes contain considerable amounts of caspase-3 and -8, whereas essential components of the mitochondrial apoptotic cascade such as caspase-9, Apaf-1 and cytochrome c were missing. Strikingly, although caspases of erythrocytes were functionally active in vitro, they failed to become activated in intact erythrocytes either during prolonged storage or in response to various proapoptotic stimuli. Following an increase of cytosolic calcium, instead the cysteine protease calpain but not caspases became activated and mediated fodrin cleavage and other morphological alterations such as cell shrinkage. Our results therefore suggest that erythrocytes do not have a functional death system. In addition, because of the presence of procaspases and the absence of a cell nucleus and mitochondria erythrocytes may be an attractive system to dissect the role of certain apoptosis-regulatory pathways. Cell Death and Differentiation (2001) 8, 1197 ± 1206.

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Section: Discussionmentioning

confidence: 99%

Human mature red blood cells express caspase-3 and caspase-8, but are devoid of mitochondrial regulators of apoptosis

et al. 2001

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“…There have been numerous studies examining the autolytic and activity state of calpain I in a variety of conditions (10,12,54,55). The mechanism(s) involved in calpain activation and activity are complex and definitive interpretations of these findings are sometimes difficult.…”

Section: Calpain I Proteolysis At Various Calcium Concentrations-mentioning

confidence: 99%

'Oxidation Inhibits Substrate Proteolysis by Calpain I but Not Autolysis

Guttmann¹,

Elce

Bell³

et al. 1997

Journal of Biological Chemistry

110

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In this study, the effects of oxidation on calpain I autolysis and calpain-mediated proteolysis were examined. Calpain I was incubated with increasing concentrations of free calcium in the presence or absence of oxidant, and autolytic conversion of both the 80-and 30-kDa subunits was measured by immunoblotting utilizing monoclonal antibodies which recognize both autolyzed and non-autolyzed forms of each subunit, respectively. Autolytic conversion of the 80-kDa subunit of calpain I was not detected until free calcium concentration was greater than 40 M, whereas autolysis of the 30-kDa subunit did not occur until the free calcium concentration was greater than 100 M. In addition, autolytic conversion of either the 80-or 30-kDa subunit was not inhibited by the presence of oxidant. Calpain I activity was measured using the fluorescent peptide N-succinyl-L-leucyl-L-leucyl-L-valyl-L-tyrosine-7-amido-4-methylcoumarin or the microtubule-associated protein tau as substrate. Calpain I was found to have proteolytic activity at free calcium concentrations below that required for autolysis. Calpain I activity was strongly inhibited by oxidant at all calcium concentrations studied, suggesting that proteolytic activity of both the non-autolyzed 80-kDa and autolyzed 76-kDa forms was susceptible to oxidation. Interestingly, whereas oxidation did not inhibit autolytic conversion, the presence of high substrate concentrations did result in a significant reduction of autolysis without altering calpain proteolytic activity. Calpain I activity that had been inhibited by the presence of oxidant was recovered immediately by addition of the reducing agent dithiothreitol.Calpains are a family of calcium-dependent thiol proteases that require both calcium and a reduced environment for activity. Calpains are present in virtually all vertebrate cells and have been postulated to play a role in many physiological processes (1-4). Calpains I and II are ubiquitously expressed, whereas the remaining isoforms are tissue-specific and are found predominantly in muscle (5, 6). Although homologous, calpains I and II require different concentrations of calcium for activity in vitro. Calpain II requires 200-1000 M calcium (7), and calpain I requires 3-50 M calcium (7) for half-maximal activity, a level which has been shown to be reached in the presynaptic terminals of neurons (8) and under pathological conditions (9). The focus of this study was calpain I because it is present in neurons and has been postulated to play a role in neuronal death associated with ischemia (10, 11) and certain neurodegenerative disorders (12-15).Calpain I is a heterodimer composed of a unique 80-kDa catalytic subunit and a 30-kDa regulatory subunit which is identical to the 30-kDa subunit of calpain II (16). How these subunits interact and what regulatory mechanisms are involved in the process of calpain activation remain unresolved. Initially it was proposed that the 80-kDa form of calpain I was an inactive pro-enzyme that must undergo calcium-dependent conformational chan...

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“…87 Reduced proteolysis with aging is most evident for long-lived proteins, some of which are known substrates for lysosomal pathways of degradation. Non-lysosomal proteolytic pathways either show very little change (ubiquitin-proteasome pathway) 88 or increase (calpains) 89 with age. Therefore, the lysosomal pathway has become the focus of investigations in pursuit of likely explanations for reduced proteolysis with age.…”

Section: Lysosomal Function During Agingmentioning

confidence: 99%

Autophagy in aging and in neurodegenerative disorders

Rajawat¹,

Bossis²

2008

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Autophagy (ATG) is the process of bulk degradation and recycling of long-lived proteins, macromolecular aggregates, and damaged intracellular organelles. Cellular homeostasis requires continuous removal of worn-out components and replacement with newly synthesized ones. Studies in yeast and other mammalian systems have increased our knowledge of the molecular mechanism of autophagy and the role of autophagy in various pathological conditions. Discovery of the genes involved in the process of autophagy has provided insight into the involvement of various molecular pathways. Growing evidence has indicated that diminished autophagic activity may play a pivotal role in the aging process. Cellular aging is characterized by a progressive accumulation of nonfunctional cellular components owing to oxidative damage and a decline in turnover rate and housekeeping mechanisms. Lysosomes are key organelles in the aging process due to their involvement in both macroautophagy and other housekeeping mechanisms. Autophagosomes themselves have limited degrading capacity and rely on fusion with lysosomes. Accumulation of defective mitochondria also appears to be critical in the progression of aging. Inefficient removal of nonfunctional mitochondria by lysosomes constitutes a major issue in the aging process. Autophagy has been associated with a growing number of pathological conditions, including cancer, myopathies, and neurodegenerative disorders. In this review, we discuss the cellular and molecular mechanisms involved in autophagy, the mechanisms of aging, and the possible role of autophagy in this process. Understanding the mechanisms by which autophagy impacts aging may provide useful molecular targets for pharmaceuticals designed to delay aging or correct conditions of premature aging.

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Calpain (Ca(2+)-dependent thiol protease) in erythrocytes of young and old individuals.

Cited by 57 publications

References 34 publications

Human mature red blood cells express caspase-3 and caspase-8, but are devoid of mitochondrial regulators of apoptosis

Human mature red blood cells express caspase-3 and caspase-8, but are devoid of mitochondrial regulators of apoptosis

'Oxidation Inhibits Substrate Proteolysis by Calpain I but Not Autolysis

Autophagy in aging and in neurodegenerative disorders

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