Role of calcium in crystallin precipitation after proteolysis by Calpain

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Abstract

Purpose. To determine the role ot calciurr in the in vjro precipitation of rat lens crystallins after proteotysis by m-calpain. Calpains are calcium-activated, neutral proteases believed to be important in many rodent models of cataract. Methods. Lens, total soluble proteins from 10-14 day-old rats were proteolyzed b> either endogenous lens m-calpain or addition of purified m-calpain In vitro light scattering at A measured precipitation of crystallins over ten days in five groups: no Ca2', continuous Ga2', Ca2' for the fifst 24 hrs only, Ca2' at 4 days, and substitute Mg2' for Ca2> after the first 24 hi. Refills. Preliminary data indicated that after proteolysis by calpain, lens crystallins precipitated most rapidly i calcium was present continuously. Removal of Ca! with EGTA after 24 hours reduced, but did not prevent the rate of precipitation of crystallins. Adding Ca2' again at 4 days, accelerated the rate of precipitation. Replacing Ca2' with Mg!<at 24 hr did not accelerate precipitation. Conclusions. Once crystallins were proteolyzed by calpain, precipitation occurred in the absence of calcium. However, Ca2+ accelerated precipitation of crystallii fragments. Factors besides Ca2+, such as exposure of hydrophobic residues on β-crystallins fragments, dimer rearrangement, or syneresis after toss it N-terminal extensions may contribute to precipitation of crystallins. These data suggest that even temporary increases In lens calcium may lead to calpain-induced opacity in rodent models.

Original languageEnglish (US)
JournalInvestigative Ophthalmology and Visual Science
Volume38
Issue number4
StatePublished - 1997

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Crystallins
Calpain
Proteolysis
Calcium
Lenses
Rodentia
Egtazic Acid
Cataract
Light
m-calpain

ASJC Scopus subject areas

  • Ophthalmology

Cite this

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title = "Role of calcium in crystallin precipitation after proteolysis by Calpain",
abstract = "Purpose. To determine the role ot calciurr in the in vjro precipitation of rat lens crystallins after proteotysis by m-calpain. Calpains are calcium-activated, neutral proteases believed to be important in many rodent models of cataract. Methods. Lens, total soluble proteins from 10-14 day-old rats were proteolyzed b> either endogenous lens m-calpain or addition of purified m-calpain In vitro light scattering at A measured precipitation of crystallins over ten days in five groups: no Ca2', continuous Ga2', Ca2' for the fifst 24 hrs only, Ca2' at 4 days, and substitute Mg2' for Ca2> after the first 24 hi. Refills. Preliminary data indicated that after proteolysis by calpain, lens crystallins precipitated most rapidly i calcium was present continuously. Removal of Ca! with EGTA after 24 hours reduced, but did not prevent the rate of precipitation of crystallins. Adding Ca2' again at 4 days, accelerated the rate of precipitation. Replacing Ca2' with Mg!2+ accelerated precipitation of crystallii fragments. Factors besides Ca2+, such as exposure of hydrophobic residues on β-crystallins fragments, dimer rearrangement, or syneresis after toss it N-terminal extensions may contribute to precipitation of crystallins. These data suggest that even temporary increases In lens calcium may lead to calpain-induced opacity in rodent models.",
author = "T. Mizuno and Shearer, {Thomas (Tom)}",
year = "1997",
language = "English (US)",
volume = "38",
journal = "Investigative Ophthalmology and Visual Science",
issn = "0146-0404",
publisher = "Association for Research in Vision and Ophthalmology Inc.",
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TY - JOUR

T1 - Role of calcium in crystallin precipitation after proteolysis by Calpain

AU - Mizuno, T.

AU - Shearer, Thomas (Tom)

PY - 1997

Y1 - 1997

N2 - Purpose. To determine the role ot calciurr in the in vjro precipitation of rat lens crystallins after proteotysis by m-calpain. Calpains are calcium-activated, neutral proteases believed to be important in many rodent models of cataract. Methods. Lens, total soluble proteins from 10-14 day-old rats were proteolyzed b> either endogenous lens m-calpain or addition of purified m-calpain In vitro light scattering at A measured precipitation of crystallins over ten days in five groups: no Ca2', continuous Ga2', Ca2' for the fifst 24 hrs only, Ca2' at 4 days, and substitute Mg2' for Ca2> after the first 24 hi. Refills. Preliminary data indicated that after proteolysis by calpain, lens crystallins precipitated most rapidly i calcium was present continuously. Removal of Ca! with EGTA after 24 hours reduced, but did not prevent the rate of precipitation of crystallins. Adding Ca2' again at 4 days, accelerated the rate of precipitation. Replacing Ca2' with Mg!2+ accelerated precipitation of crystallii fragments. Factors besides Ca2+, such as exposure of hydrophobic residues on β-crystallins fragments, dimer rearrangement, or syneresis after toss it N-terminal extensions may contribute to precipitation of crystallins. These data suggest that even temporary increases In lens calcium may lead to calpain-induced opacity in rodent models.

AB - Purpose. To determine the role ot calciurr in the in vjro precipitation of rat lens crystallins after proteotysis by m-calpain. Calpains are calcium-activated, neutral proteases believed to be important in many rodent models of cataract. Methods. Lens, total soluble proteins from 10-14 day-old rats were proteolyzed b> either endogenous lens m-calpain or addition of purified m-calpain In vitro light scattering at A measured precipitation of crystallins over ten days in five groups: no Ca2', continuous Ga2', Ca2' for the fifst 24 hrs only, Ca2' at 4 days, and substitute Mg2' for Ca2> after the first 24 hi. Refills. Preliminary data indicated that after proteolysis by calpain, lens crystallins precipitated most rapidly i calcium was present continuously. Removal of Ca! with EGTA after 24 hours reduced, but did not prevent the rate of precipitation of crystallins. Adding Ca2' again at 4 days, accelerated the rate of precipitation. Replacing Ca2' with Mg!2+ accelerated precipitation of crystallii fragments. Factors besides Ca2+, such as exposure of hydrophobic residues on β-crystallins fragments, dimer rearrangement, or syneresis after toss it N-terminal extensions may contribute to precipitation of crystallins. These data suggest that even temporary increases In lens calcium may lead to calpain-induced opacity in rodent models.

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