Band 3 protein degradation by calpain is enhanced in erythrocytes of old people.
Band 3 protein is a major erythrocyte transmembrane glycoprotein. We compared the degradation of band 3 protein by calpain I (a cytoplasmic, micromolar-Ca2(+)-requiring thiol proteinase) in the cells from old individuals (greater than 70 years old) to that in the cells from young ones (20-30 years old). In the young, little degradation of band 3 protein occurred in calpain-treated erythrocyte ghosts. In the old, significant band 3 protein degradation was found in erythrocyte ghosts treated similarly. The difference between young and old in the susceptibility of band 3 protein to calpain was retained in membrane vesicles (membranes stripped of peripheral proteins by NaOH) and in chymotrypsin-generated 60 kDa fragment (CH-60). The isolated N-terminal cytoplasmic 43 kDa fragment was degraded by calpain to a similar extent in old and in young. The separated 17 kDa membrane domain of the CH-60 and the trypsin-generated C-terminal 55 kDa membrane-spanning fragment were not degraded by calpain I in the young, nor in the old. Thus the N-terminal cytoplasmic domain is the domain degraded by calpain I. Enhanced sensitivity in the old is observed in intact band 3 protein and in CH-60, the isolated cytoplasmic domain being equally susceptible in young and old. The observed age-related enhanced sensitivity to calpain is consistent with the presence of modifications in band 3 protein and alterations in the association with the calpain-calpastatin system. Band 3 protein has several important functions, with modifications in the protein having implications for altered cell behaviour in the old individual.
Schwarz-Ben Meir
N
N
Department of Human Genetics, Sackler School of Medicine, Tel-Aviv University, Israel.
Glaser
T
T
Kosower
N S
NS
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood*; D001457:Anion Exchange Protein 1, Erythrocyte / Q000378:metabolism*; D002154:Calpain / Q000378:metabolism*; D002918:Chymotrypsin / Q000378:metabolism; D004910:Erythrocyte Membrane / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D008565:Membrane Proteins / Q000097:blood; D008970:Molecular Weight; D010446:Peptide Fragments / Q000097:blood
D001457:Anion Exchange Protein 1, Erythrocyte; D008565:Membrane Proteins; D010446:Peptide Fragments; D002918:Chymotrypsin; D002154:Calpain