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Plasma membrane Ca-ATPase isoform expression in human cataractous lenses compared to age-matched clear lenses

Moazez J Marian1, Partha Mukhopadhyay, Douglas Borchman

  • 1Department of Biochemistry and Molecular Biology, University of Louisville, Louisville, Ky, USA.

Ophthalmic Research
|January 29, 2008
PubMed

Insights

Plasma membrane calcium ATPase (PMCA) pump levels in the lens were investigated. Cataractous lenses showed significantly higher PMCA2 expression, suggesting a compensatory response to elevated intracellular calcium.

Area of Science:

  • Ophthalmology
  • Cell Biology
  • Biochemistry

Background:

  • The plasma membrane calcium ATPase (PMCA) pump is crucial for calcium extrusion from cells.
  • Calcium homeostasis is vital for lens transparency and function.
  • Age-related changes and opacity in the lens may affect calcium regulation.

Purpose of the Study:

  • To investigate age- and opacity-related changes in PMCA isoform mRNA and protein levels in human lenses.
  • To determine the role of PMCA pumps in lens calcium regulation, particularly in cataracts.

Main Methods:

  • Quantitative real-time reverse transcription polymerase chain reaction (RT-PCR) for mRNA analysis.
  • Western blot analysis for PMCA protein quantification.
  • Comparison of PMCA expression in cataractous versus age-matched clear human lenses.

Main Results:

  • No PMCA mRNA or protein was detected in human lens fiber cells.
  • PMCA1, PMCA3, and PMCA4 mRNA and protein levels were similar in the epithelium of cataractous and clear lenses.
  • PMCA2 mRNA and protein levels were significantly elevated (1.6-2.5 times higher) in the epithelium of cataractous lenses compared to age-matched clear lenses.

Conclusions:

  • PMCA2 upregulation in cataractous lenses may represent a compensatory mechanism to manage increased intracellular calcium.
  • PMCA isoforms exhibit differential expression patterns in the lens epithelium related to cataract formation.
  • Understanding PMCA's role in lens calcium homeostasis could offer insights into cataract pathogenesis.

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