Alpha A- and alpha B-crystallin in the retina. Association with the post-Golgi compartment of frog retinal photoreceptors

J Biol Chem. 1994 Jun 17;269(24):16853-61.

Abstract

alpha A- and alpha B-Crystallins are significant contributors to maintaining the transparency of the vertebrate lens. We have found that both alpha A- and alpha B-crystallins are also present, at approximately equimolar concentrations, in frog retinal cells. They were identified by sequencing portions of each polypeptide, by immunochemical cross-reactivity with antibodies to bovine alpha-crystallins, and by their relative mobility in two-dimensional gel electrophoresis. Retinal alpha-crystallins form macromolecular multimeric complexes similar to those found in the lens, and they are abundant both in soluble and membrane-associated forms. A surprising finding is that alpha-crystallins bind specifically to the photoreceptor post-Golgi membranes that mediate transport of newly synthesized rhodopsin. Upon treatment of post-Golgi membranes with urea or Triton X-114, a portion of the bound alpha B-crystallin remains tightly associated, indicating that the alpha B-form may mediate membrane binding of an alpha-crystallin multimeric complex. Both subunits are synthesized in vitro by isolated frog retinas, but alpha B-crystallin appears to have a higher renewal rate. Newly synthesized alpha-crystallins become associated with the post-Golgi membranes concurrently with newly synthesized rhodopsin. Association of alpha-crystallins with newly synthesized rhodopsin suggests that they may participate in photoreceptor outer segment membrane renewal. Our findings implicate an important function for both alpha A- and alpha B-crystallins in the same, extralenticular, tissue.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cattle
  • Cricetinae
  • Crystallins / analysis*
  • Crystallins / chemistry*
  • Crystallins / ultrastructure
  • Electrophoresis, Gel, Two-Dimensional
  • Electrophoresis, Polyacrylamide Gel
  • Golgi Apparatus / chemistry*
  • Intracellular Membranes / chemistry*
  • Molecular Sequence Data
  • Molecular Weight
  • Peptide Fragments / chemistry
  • Peptide Fragments / isolation & purification
  • Photoreceptor Cells / chemistry*
  • Protein Binding
  • Ranidae
  • Retina / chemistry*
  • Sequence Homology, Amino Acid
  • Subcellular Fractions / chemistry

Substances

  • Crystallins
  • Peptide Fragments