April 2009
Volume 50, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2009
A-Crystallin and B-Crystallin Are Synthesized in Separate Subcellular Compartments in the Ocular Lens
Author Affiliations & Notes
  • R. K. Gangalum
    Jules Stein Eye Institute, Geffen School of Medicine @ UCLA, Los Angeles, California
  • J. Horwitz
    Jules Stein Eye Institute, Geffen School of Medicine @ UCLA, Los Angeles, California
  • S. P. Bhat
    Jules Stein Eye Institute, Geffen School of Medicine @ UCLA, Los Angeles, California
    Brain Research Institute, Molecular Biology Institute, UCLA, Los Angeles, California
  • Footnotes
    Commercial Relationships  R.K. Gangalum, None; J. Horwitz, None; S.P. Bhat, None.
  • Footnotes
    Support  NIH Grant R01 EY006044
Investigative Ophthalmology & Visual Science April 2009, Vol.50, 1636. doi:
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      R. K. Gangalum, J. Horwitz, S. P. Bhat; A-Crystallin and B-Crystallin Are Synthesized in Separate Subcellular Compartments in the Ocular Lens. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1636.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: : A-crystallin (A) and B-crystallin (B) are historically considered to be the two subunits of a single protein, -crystallin. Both these small heat shock proteins are expressed in non-lenticular tissues, however they are not found together in the same tissue suggesting that they function as independent proteins. Outside of the lens, A is expressed predominantly in spleen and thymus, where no B is detected. B, on the other hand is highly expressed in the heart, where A is not found (J Biol. Chem. 267:23337-41, 1992). We have previously suggested that these two proteins may also have independent physiological functions inside the ocular lens (Eur. J. Biochem. 102: 775-81, 1991). In this investigation we have examined the status of A and B synthesis and localization in the developing rat lens.

Methods: : Differential centrifugation and discontinuous density sucrose gradient fractionation were employed to study the association of A and B in different cellular compartments at various developmental stages. Free and bound polysomes were fractionated and the presence of A and B in each of these compartments was investigated. Immunoflourescence and confocal microscopy were used to localize the A and B in the lens epithelial cells and in the native ocular lens.

Results: : Differential centrifugation shows that in postnatal day 3 (PND3) and PND10 lenses significantly more of B is found in the membrane fractions than A. Density gradient fractionation of post-nuclear supernatants reveals that A like B is associated with the Golgi membranes. Interestingly, examination of free and bound polyribosome fractions isolated from fetal and post-natal day 10 rat lenses reveals that A is associated with free polysomes and smooth membranes while B is predominantly found in the bound polysome fractions.

Keywords: crystallins • protein structure/function • gene/expression 
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