title: Degradation of unassembled alpha- and beta-spectrin by distinct intracellular pathways: regulation of spectrin topogenesis by beta-spectrin degradation.
abstract: 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.
authors.forename: C M
authors.initials: CM
authors.lastname: Woods
authors.forename: E
authors.initials: E
authors.lastname: Lazarides
mesh_terms: D000613:Aminobutyrates / Q000097:blood; D000818:Animals; D002154:Calpain; D002172:Canavanine / Q000097:blood; D002642:Chick Embryo; D003593:Cytoplasm / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D010450:Endopeptidases / Q000097:blood; D004910:Erythrocyte Membrane / Q000378:metabolism / Q000648:ultrastructure; D004912:Erythrocytes / Q000378:metabolism*; D006207:Half-Life; D006863:Hydrogen-Ion Concentration; D008247:Lysosomes / Q000378:metabolism; D046911:Macromolecular Substances; D010446:Peptide Fragments / Q000097:blood; D010447:Peptide Hydrolases / Q000097:blood; D013049:Spectrin / Q000378:metabolism*; D014357:Trypsin / Q000378:metabolism
chemical_list: D000613:Aminobutyrates; D046911:Macromolecular Substances; D010446:Peptide Fragments; D013049:Spectrin; C002832:2-amino-3-chlorobutyric acid; D002172:Canavanine; D010450:Endopeptidases; D010447:Peptide Hydrolases; D014357:Trypsin; D002154:Calpain