Human and monkey lenses cultured with calcium ionophore form αB-crystallin lacking the c-terminal lysine, a prominent feature of some human cataracts

Emi Nakajima, Larry David, Michael A. Riviere, Mitsuyoshi Azuma, Thomas (Tom) Shearer

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9 Citations (Scopus)

Abstract

Purpose. Elevation of lens calcium occurs in both human and experimental animal cataracts, and opacification may result from calcium-activated proteolysis. The purpose of the present study was to determine whether calcium accumulation in cultured human and Macaca mulatta lenses results in proteolysis of crystallins, the major lens proteins.Methods.Two-dimensional electrophoresis and mass spectrometry were used to construct detailed maps of human and monkey lens crystallins so that proteolysis after calcium accumulation could be monitored and the altered crystallins identified. Human and macaque lenses cultured in A23187 showed elevated lenticular calcium and superficial cortical opacities. The carboxypeptidase E (CPE) gene is expressed in human lens, and its presence in lens fibers was demonstrated by Western blot. To investigate whether CPE could cause similar truncation, purified αB-crystallin and CPE were incubated in vitro. Results. The major change observed in the crystallins of these cultured lenses was the accumulation of αB1-174-crystallin resulting from the loss of a C-terminal lysine. This result was significant, because similar appearance of αB1-174 is a prominent change in some human cataracts. αB-crystallin and CPE incubation result in the formation of αB1-174-crystallin. This truncation was specific to αB1174-crystallin, since other crystallins were not proteolyzed. Although a weaker activator than zinc, calcium activated CPE in vitro. Conclusions. Since zinc concentrations did not increase during culture in A23187, calcium uptake in the lens may be responsible for CPE activation and αB1174 formation during cataract.

Original languageEnglish (US)
Pages (from-to)5828-5836
Number of pages9
JournalInvestigative Ophthalmology and Visual Science
Volume50
Issue number12
DOIs
StatePublished - Dec 2009

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Crystallins
Calcium Ionophores
Cataract
Lenses
Lysine
Haplorhini
Carboxypeptidase H
Calcium
Proteolysis
Calcimycin
Zinc
Macaca
Macaca mulatta
Electrophoresis
Mass Spectrometry
Western Blotting

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience
  • Medicine(all)

Cite this

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title = "Human and monkey lenses cultured with calcium ionophore form αB-crystallin lacking the c-terminal lysine, a prominent feature of some human cataracts",
abstract = "Purpose. Elevation of lens calcium occurs in both human and experimental animal cataracts, and opacification may result from calcium-activated proteolysis. The purpose of the present study was to determine whether calcium accumulation in cultured human and Macaca mulatta lenses results in proteolysis of crystallins, the major lens proteins.Methods.Two-dimensional electrophoresis and mass spectrometry were used to construct detailed maps of human and monkey lens crystallins so that proteolysis after calcium accumulation could be monitored and the altered crystallins identified. Human and macaque lenses cultured in A23187 showed elevated lenticular calcium and superficial cortical opacities. The carboxypeptidase E (CPE) gene is expressed in human lens, and its presence in lens fibers was demonstrated by Western blot. To investigate whether CPE could cause similar truncation, purified αB-crystallin and CPE were incubated in vitro. Results. The major change observed in the crystallins of these cultured lenses was the accumulation of αB1-174-crystallin resulting from the loss of a C-terminal lysine. This result was significant, because similar appearance of αB1-174 is a prominent change in some human cataracts. αB-crystallin and CPE incubation result in the formation of αB1-174-crystallin. This truncation was specific to αB1174-crystallin, since other crystallins were not proteolyzed. Although a weaker activator than zinc, calcium activated CPE in vitro. Conclusions. Since zinc concentrations did not increase during culture in A23187, calcium uptake in the lens may be responsible for CPE activation and αB1174 formation during cataract.",
author = "Emi Nakajima and Larry David and Riviere, {Michael A.} and Mitsuyoshi Azuma and Shearer, {Thomas (Tom)}",
year = "2009",
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language = "English (US)",
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pages = "5828--5836",
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TY - JOUR

T1 - Human and monkey lenses cultured with calcium ionophore form αB-crystallin lacking the c-terminal lysine, a prominent feature of some human cataracts

AU - Nakajima, Emi

AU - David, Larry

AU - Riviere, Michael A.

AU - Azuma, Mitsuyoshi

AU - Shearer, Thomas (Tom)

PY - 2009/12

Y1 - 2009/12

N2 - Purpose. Elevation of lens calcium occurs in both human and experimental animal cataracts, and opacification may result from calcium-activated proteolysis. The purpose of the present study was to determine whether calcium accumulation in cultured human and Macaca mulatta lenses results in proteolysis of crystallins, the major lens proteins.Methods.Two-dimensional electrophoresis and mass spectrometry were used to construct detailed maps of human and monkey lens crystallins so that proteolysis after calcium accumulation could be monitored and the altered crystallins identified. Human and macaque lenses cultured in A23187 showed elevated lenticular calcium and superficial cortical opacities. The carboxypeptidase E (CPE) gene is expressed in human lens, and its presence in lens fibers was demonstrated by Western blot. To investigate whether CPE could cause similar truncation, purified αB-crystallin and CPE were incubated in vitro. Results. The major change observed in the crystallins of these cultured lenses was the accumulation of αB1-174-crystallin resulting from the loss of a C-terminal lysine. This result was significant, because similar appearance of αB1-174 is a prominent change in some human cataracts. αB-crystallin and CPE incubation result in the formation of αB1-174-crystallin. This truncation was specific to αB1174-crystallin, since other crystallins were not proteolyzed. Although a weaker activator than zinc, calcium activated CPE in vitro. Conclusions. Since zinc concentrations did not increase during culture in A23187, calcium uptake in the lens may be responsible for CPE activation and αB1174 formation during cataract.

AB - Purpose. Elevation of lens calcium occurs in both human and experimental animal cataracts, and opacification may result from calcium-activated proteolysis. The purpose of the present study was to determine whether calcium accumulation in cultured human and Macaca mulatta lenses results in proteolysis of crystallins, the major lens proteins.Methods.Two-dimensional electrophoresis and mass spectrometry were used to construct detailed maps of human and monkey lens crystallins so that proteolysis after calcium accumulation could be monitored and the altered crystallins identified. Human and macaque lenses cultured in A23187 showed elevated lenticular calcium and superficial cortical opacities. The carboxypeptidase E (CPE) gene is expressed in human lens, and its presence in lens fibers was demonstrated by Western blot. To investigate whether CPE could cause similar truncation, purified αB-crystallin and CPE were incubated in vitro. Results. The major change observed in the crystallins of these cultured lenses was the accumulation of αB1-174-crystallin resulting from the loss of a C-terminal lysine. This result was significant, because similar appearance of αB1-174 is a prominent change in some human cataracts. αB-crystallin and CPE incubation result in the formation of αB1-174-crystallin. This truncation was specific to αB1174-crystallin, since other crystallins were not proteolyzed. Although a weaker activator than zinc, calcium activated CPE in vitro. Conclusions. Since zinc concentrations did not increase during culture in A23187, calcium uptake in the lens may be responsible for CPE activation and αB1174 formation during cataract.

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SN - 0146-0404

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