Molecular identification and expression of erythroid K:Cl cotransporter in human and mouse erythroleukemic cells.
A major pathway for K+ efflux in human reticulocytes and young RBCs is K:Cl cotransport (K:Cl-CT). The activity of K:Cl-CT is increased in pathologic RBCs containing hemoglobins S and C and may contribute to the abnormal dehydration state of these cells. Human K:Cl-CT (gene product KCC1) has been recently sequenced from human (hKCC1), rabbit and rat tissue by Gillen et al. (J Biol Chem 271:16237, 1996). We report here the sequence of KCC1 from human and mouse erythroleukemic cells (K562 and MEL cells, respectively). The cDNA for human erythroid- KCC1 is 100% identical to hKCC1 and the cDNA for mouse erythroid- KCC1 shares 89% identity with hKCC1, which translates to 96% identity at the amino acid level. Mammalian KCC1 is strongly conserved with >95% identity between human, rabbit, rat, and mouse KCC1 proteins. We did not detect any full-length mRNA transcripts of human erythroid- KCC1 in circulating reticulocytes. We detected two mRNA isoforms of human erythroid- KCC1 that resulted in C-terminal truncated proteins (73 amino acid and 17 amino acids, respectively). Human and mouse erythroidKCC1 differed at several consensus sites including a predicted PKC phosphorylation site at 108threonine and a predicted CK2 phosphorylation site at 51serine, within the predicted cytoplasmic N-terminal, that are present in human but not mouse erythroid- KCC1. Expression of MEL- KCC1 mRNA increases substantially upon DMSO- induced differentiation opening the possibility that erythroid- KCC1 plays a role in early erythroid maturation events. The molecular identification of erythroid- KCC1 is an important step towards understanding the physiologic role mediated by this protein in young and pathologic RBCs and during erythropoiesis, as well as providing a new tool for the elucidation of pathways and signals involved in RBC volume regulation.[1]References
- Molecular identification and expression of erythroid K:Cl cotransporter in human and mouse erythroleukemic cells. Pellegrino, C.M., Rybicki, A.C., Musto, S., Nagel, R.L., Schwartz, R.S. Blood Cells Mol. Dis. (1998) [Pubmed]
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