Tyrosine-protein kinase inhibition in human erythrocytes by polyphosphoinositides (PIP and PIP2).
In human erythrocytes Ser/Thr- and Tyr-phosphorylations of cytoplasmic domain of band 3 are catalyzed by casein kinase I and Tyr-protein kinase respectively, both distributed between cytosol and membrane structures. The results reported here show that purified cytosolic Tyr-protein kinase activity, assayed on added substrates such as poly(Glu,Tyr)4:1 and isolated chymotryptic fragments of band 3 cytoplasmic domain (cdb3), is potently inhibited by PIP and even more by PIP2. Similar inhibitory effects are displayed by these polyphosphoinositides also on the endogenous Tyr-phosphorylation of band 3, when they are added to the isolated native membranes, thus suggesting their involvement in regulating in-vivo Tyr-phosphorylation of membrane proteins.
Bordin
L
L
Istituto di Medicina Interna, Università di Padova, Italy.
Clari
G
G
Baggio
B
B
Moret
V
V
D000255:Adenosine Triphosphate / Q000378:metabolism; D001457:Anion Exchange Protein 1, Erythrocyte / Q000378:metabolism; D002918:Chymotrypsin / Q000378:metabolism; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D010446:Peptide Fragments / Q000097:blood; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols / Q000494:pharmacology*; D010768:Phosphoserine / Q000378:metabolism; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000097:blood; D014443:Tyrosine / Q000031:analogs & derivatives / Q000097:blood
D001457:Anion Exchange Protein 1, Erythrocyte; D010446:Peptide Fragments; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; C037178:phosphatidylinositol 4-phosphate; D010768:Phosphoserine; D019000:Phosphotyrosine; D014443:Tyrosine; D000255:Adenosine Triphosphate; D011505:Protein-Tyrosine Kinases; D002918:Chymotrypsin