Calcium-induced degradation of the lens cytoskeleton

Marcantonio, Julia M.; Duncan, G.

doi:10.1042/bst0191148

Cited by 20 publications

(19 citation statements)

References 5 publications

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“…At the end of the incubation time, lenses were homogenized in sample buffer (2 ml) which contains protease inhibitor leupeptin (Sigma, St. Louis, MO., 0.1 mM), then centriftiged at 37,000 x g (23). Supernatant (20 μΐ) was run on 10% SDS-PAGE and gel was transferred to a nitrocellulose by following the immunoblotting procedure (34).…”

Section: Immunoblotting Of Lens Fodrinmentioning

confidence: 99%

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Modelling cortical cataractogenesis XXIX. Calpain proteolysis of lens fodrin in cataract

Kilic

Trevithick

1998

IUBMB Life

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SUMMARYThe relation between cataract and calpain proteolysis of lens fodrin was studied in two systems: elevated glucose (55.6 mM, diabetic model), and cytochalasin D (CD, 10 2 mM, actin depolymerization-induced opacity model). Glucose treatment (48 h) caused a visible opaque layer and enzyme leakage, with a concomitant accumulation of ([Ca2+]¡) around the lens equatorial cortex. CD caused both earlier and greater opacity and enzyme leakage than glucose. Lens fodrin digestion occurred in parallel with the timing and extent of calcium elevation. A calpain inhibitor peptide (CIP, 10" 2 mM) reduced the proteolysis of fodrin, opacity, and enzyme leakage in glucose-treated lenses but only partially retarded them in CDtreated lenses. These results suggest a mechanism in which calpain proteolysis of fodrin is a critical event in lens damage during opacification of cortical cataract.

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Section: Immunoblotting Of Lens Fodrinmentioning

confidence: 99%

“…Spectrin/fodrin was the first to be described to undergo calpain-catalyzed proteolysis in many tissues (14). In the lens both a-fodrin and a-, /3-spectrin were identified (20,21) and studied (22,23). Despite the elucidation of the biochemical role and characteristics of calpain in various tissues, surprisingly, in the lens these still remain controversial.…”

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confidence: 99%

Modelling cortical cataractogenesis XXIX. Calpain proteolysis of lens fodrin in cataract

Kilic

Trevithick

1998

IUBMB Life

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“…Disturbances in calcium homeostasis result in the activation of several calcium-dependent enzymes including calpains [1,4]. With increasing age, proteasome activity may decrease, leading to deficient removal of old proteins, which in turn may cause cataract [5].…”

Section: Introductionmentioning

confidence: 99%

A New Model for Assessing Proteolysis in the Intact Mouse Lens in Organ Culture

et al. 2004

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Purpose: To develop a new method to investigate proteolysis in the intact lens in organ culture. Methods: Intact mouse lenses were assayed at regular intervals for proteolytic activity using fluorogenic peptide substrates ± addition of ionomycin. Specific inhibitors were used to determine the activity of calpains, the proteasome and acid lysosomal enzymes. Results: Significant levels of proteolytic activity were present in the intact lens. Proteolysis was stimulated by ionomycin. Preincubation with an inhibitor to the proteasome significantly decreased proteolysis whereas inhibitors of calpain and acid lysosomal enzymes did not. Conclusion: This study indicates that in the intact mouse lens in culture, the proteasome is an important protease. Its activity is at least partially regulated by calcium.

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“…The second is selective retention of the in serted components in their functional posi tions in that domain. Targeted delivery is brought about largely by vesicular traffic along cytoplasmic microtubules and actin fi laments [1,2], Selective retention frequently depends on protein anchorage onto the submembranous cytoskeleton [3], In addition, re cent evidence indicates that the state of poly merisation ofcvtoskeletal filaments can affect channel activation [4], We have previously shown that increased calcium leads to degra dation of cytoskeletal proteins in both whole lenses and native lens homogenates, using bo vine and rat models [5,6], The aim of the present study was to investigate normal cytoskcletal structure in freshly isolated human lens epithelia, and to follow any changes to this structure induced by an increase in cell calcium.…”

Section: Introductionmentioning

confidence: 99%

Calcium-Induced Disruption of the Lens Cytoskeleton

Marcantonio¹

1996

Ophthalmic Res

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Ionic homeostasis is essential to lens clarity and the lens epithelium plays a large part in homeostasis, through vectorial transport. In most epithelia maintenance of vectorial function depends on the cytoskeleton. Capsule/epithelium preparations from human donor lenses have been used for immunohisto-chemical investigations of both normal epithelial cell cytoskeletal structure, and of structural changes induced by increasing cell calcium. A sustained increase in intracellular calcium, induced by incubation with A23187 and W7, led to a loss of cytoskeletal organisation. Changes included depolymerisation of cytoplasmic actin filaments, disaggregation of microtubules and initial thickening, followed by breakdown, of vimentin intermediate filaments. In addition, spectrin staining, normally confined to the basal-lateral plasma membranes, became diffuse within the cytoplasm. Such disruptions of cytoskeletal structure would decrease ionic control, leading to increasing osmotic stress.

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Calcium-induced degradation of the lens cytoskeleton

Cited by 20 publications

References 5 publications

Modelling cortical cataractogenesis XXIX. Calpain proteolysis of lens fodrin in cataract

Modelling cortical cataractogenesis XXIX. Calpain proteolysis of lens fodrin in cataract

A New Model for Assessing Proteolysis in the Intact Mouse Lens in Organ Culture

Calcium-Induced Disruption of the Lens Cytoskeleton

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