One of the most intensively studied post-translational modifications of erythrocyte proteins is the phosphorylation of @entity669 residues of band 3, which is strictly regulated in vivo by PTKs (protein- @entity669 kinases) and PTPs (protein- @entity10393 phosphatases). Two PTKs ( @entity13132 (syk) and p56/53(lyn)) and two PTP activities ( @entity4641 and @entity9702 ) have been immunologically identified so far in mature @entity1 erythrocytes. We have shown previously that band 3 undergoes @entity669 phosphorylation upon a decrease in cell volume, as occurs when erythrocytes treated with @entity141 / @entity141 ionophore ( @entity3365 ) lose KCl and release microvesicles. Similar levels of band 3 @entity669 phosphorylation in vesicles and in the parent cells are induced by this treatment. However, we have found that @entity669 phosphorylation of band 3 in vesicles is more stable than in whole erythrocytes. Examination of how the identified PTPs and PTKs are partitioned between the vesicles and the remnant cells during vesiculation reveals that @entity4641 , unlike the PTKs, is retained entirely in the parent cell compartment. Since a tight association between @entity4641 and band 3 has been documented previously, we have investigated the partitioning of @entity4641 and band 3 between the membrane and the membrane-skeletal fractions prepared from resting or @entity141 / @entity3365 -treated cells. Our results rule out the possibility that the preferential retention of @entity4641 within the cell was due to an increase in the amount of membrane-skeleton-associated band 3 (and of @entity4641 ) during the release of spectrin-free vesicles, suggesting a more complex modality of interaction of @entity4641 with band 3 in the erythrocyte membrane. Analysis of erythrocytes of different cell ages revealed that @entity4641 , unlike the other enzymes examined, was quantitatively conserved during erythrocyte aging. This suggests important roles for the down-regulation of @entity669 phosphorylation of band 3 in erythrocyte physiology, and for vesiculation as a mechanism of @entity1 erythrocyte senescence.

Differential sorting of @entity669 kinases and @entity10393 phosphatases acting on band 3 during vesiculation of XXXX erythrocytes.

@entity1 :: ('9606', 'Species') :: ['human'] @entity9702 :: ('5781', 'Gene') :: ['SHPTP-2'] @entity13132 :: ('10521', 'Gene') :: ['p72'] @entity10393 :: ('CHEBI:74956', 'Chemical') :: ['phosphotyrosine'] @entity4641 :: ('5770', 'Gene') :: ['PTP1B'] @entity3365 :: ('MESH:D000001', 'Chemical') :: ['A23187'] @entity141 :: ('CHEBI:29108', 'Chemical') :: ['Ca(2+)'] @entity669 :: ('CHEBI:18186', 'Chemical') :: ['tyrosine']
@entity1 :: (9606,Species) :: ['human']
