title: Protein kinases and membrane protein phosphorylation in normal and abnormal human erythrocytes: variation related to mean cell age.
abstract: Protein kinase activities and membrane autophosphorylation reactions of normal and abnormal human erythrocytes were analyzed. Erythrocytes from patients with high reticulocytosis due to sickle cell anemia and other disorders (n = 13) exhibited elevated activities of total and membrane-bound cAMP-independent casein kinase and cAMP-stimulated histone kinase. Relative to normal controls (n = 10), the average total activities in these abnormal cells were increased 50% and 81%, respectively. The casein and histone kinase activities of normal and abnormal erythrocytes declined significantly with increasing age and buoyant density in Stractan density gradients. Casein kinase activity was highly correlated (r = 0.88; n = 23) with the percentage of reticulocytes in the fraction, consistent with either a progressive loss of activity in mature erythrocytes or an abrupt decline during reticulocyte maturation. The cAMP-independent and cAMP-stimulated autophosphorylation activities of isolated membranes also declined with increasing erythrocyte age. On average, the initial rate of spectrin labeling was 36% lower in ghosts from Stractan gradient bottom fractions, relative to ghosts from top fractions similarly incubated with gamma-32P-ATP. Incorporation into the "band 4.5 zone" (primarily labeling bands 4.8 and 4.9, mol wt 47,800 and 44,600) was also age-dependent. In membranes of unfractionated sickle cells, spectrin autophosphorylation was within normal limits, while 4.5 zone autophosphorylation was increased. Membranes from high reticulocytosis controls (vitamin B-12 deficiency) exhibited similar autophosphorylation patterns, suggesting that the altered autophosphorylation pattern of sickle cell membranes may be attributed to the predominance of very young cells.
mesh_terms: D000755:Anemia, Sickle Cell / Q000201:enzymology; D004905:Erythrocyte Aging; D004910:Erythrocyte Membrane / Q000378:metabolism*; D004912:Erythrocytes / Q000201:enzymology* / Q000378:metabolism*; D004913:Erythrocytes, Abnormal / Q000201:enzymology*; D006801:Humans; D010766:Phosphorylation; D011494:Protein Kinases / Q000097:blood*; D012156:Reticulocytes / Q000166:cytology / Q000201:enzymology
chemical_list: D011494:Protein Kinases