title: Molecular identification and expression of erythroid K:Cl cotransporter in human and mouse erythroleukemic cells.
abstract: 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.
authors.affiliation: Division of Hematology, Albert Einstein College of Medicine-Montefiore Medical Center, 111 East 210th Street, Bronx, NY, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Pellegrino
authors.forename: A C
authors.initials: AC
authors.lastname: Rybicki
authors.forename: S
authors.initials: S
authors.lastname: Musto
authors.forename: R L
authors.initials: RL
authors.lastname: Nagel
authors.forename: R S
authors.initials: RS
authors.lastname: Schwartz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000097:blood*; D002712:Chlorides / Q000097:blood*; D003001:Cloning, Molecular; D004905:Erythrocyte Aging / Q000502:physiology; D006801:Humans; D004915:Leukemia, Erythroblastic, Acute / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D011188:Potassium / Q000097:blood*; D011487:Protein Conformation; D012156:Reticulocytes / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D027981:Symporters; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D000096922:K Cl- Cotransporters
chemical_list: D002352:Carrier Proteins; D002712:Chlorides; D011188:Potassium; D027981:Symporters; D000096922:K Cl- Cotransporters