Degradation of unassembled alpha- and beta-spectrin by distinct intracellular pathways: regulation of spectrin topogenesis by beta-spectrin degradation

Cell. 1985 Apr;40(4):959-69. doi: 10.1016/0092-8674(85)90356-3.


Analysis of the turnover of unassembled proteins during the assembly of the erythroid membrane skeleton has revealed that alpha- and beta-spectrin, two structurally related, high molecular weight proteins, are degraded in a selective manner by two distinct intracellular pathways. Unassembled alpha-spectrin (t1/2 approximately equal to 2 hr) is degraded by a system with all the pharmacological characteristics of a membrane-bound, lysosomal-type pathway. This result illustrates for the first time the selective degradation of an intracellular short-lived, unassembled protein by a lysosomal pathway. In contrast, unassembled beta-spectrin is degraded extremely rapidly (t1/2 approximately equal to 15-20 min at 38 degrees C) by a soluble cytoplasmic system in an apparently ATP-independent manner. These observations suggest that the selective and rapid degradation of beta-spectrin serves an important regulatory role in the topogenesis of the spectrin-based membrane skeleton in the chicken erythrocyte.

Publication types

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

MeSH terms

  • Aminobutyrates / blood
  • Animals
  • Calpain
  • Canavanine / blood
  • Chick Embryo
  • Cytoplasm / metabolism
  • Cytoskeleton / metabolism
  • Endopeptidases / blood
  • Erythrocyte Membrane / metabolism
  • Erythrocyte Membrane / ultrastructure
  • Erythrocytes / metabolism*
  • Half-Life
  • Hydrogen-Ion Concentration
  • Lysosomes / metabolism
  • Macromolecular Substances
  • Peptide Fragments / blood
  • Peptide Hydrolases / blood
  • Spectrin / metabolism*
  • Trypsin / metabolism


  • Aminobutyrates
  • Macromolecular Substances
  • Peptide Fragments
  • Spectrin
  • 2-amino-3-chlorobutyric acid
  • Canavanine
  • Endopeptidases
  • Peptide Hydrolases
  • Trypsin
  • Calpain