Synthesis, assembly, and turnover of alpha and beta-erythroid and nonerythroid spectrins in rat hippocampal neurons.
The synthesis and turnover of alpha-erythroid, beta-erythroid, alpha-nonerythroid and beta-nonerythroid spectrins was investigated in cultured rat hippocampal neurons. [35S]methionine and subunit specific antibodies were used to label and immunoprecipitate newly synthesized spectrins in 12- to 14-day-old cultures. Synthesis experiments, performed under normal resting conditions, showed that the ratio of newly synthesized alpha-erythroid/beta-erythroid and alpha-nonerythroid/beta-nonerythroid spectrins is 1/1 (mol/mol) both in the soluble and insoluble fractions. Soluble and insoluble alpha and beta erythroid spectrin turn over rapidly (half-life=16-24 min). Soluble nonerythroid alpha-spectrin (half-life=80 min) and beta spectrin (half-life=53 min) turn over more slowly than their insoluble counterparts (30-34 min). The nonerythroid alpha spectrin turnover was significantly different (p<0.05) from the other measurements except for nonerythroid beta spectrin, indicating that these subunits are protected from rapid proteolytic degradation until they are assembled in the membrane skeleton.
Sangerman
J
J
Department of Structural Biology, University of South Alabama College of Medicine, MSB 2042, Mobile, AL, USA.
Gard
A L
AL
Shah
A
A
Goodman
S R
SR
D000818:Animals; D000831:Animals, Newborn; D002352:Carrier Proteins / Q000096:biosynthesis / Q000378:metabolism*; D002478:Cells, Cultured; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000096:biosynthesis / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D008840:Microfilament Proteins / Q000096:biosynthesis / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D013049:Spectrin / Q000096:biosynthesis / Q000378:metabolism*; D013462:Sulfur Radioisotopes; D013997:Time Factors
D002352:Carrier Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D008715:Methionine; D008840:Microfilament Proteins; D013049:Spectrin; D013462:Sulfur Radioisotopes; C041393:spectrin-like proteins