Expression of multiple Na+,K+-adenosine triphosphatase isoform genes in human hematopoietic cells. Behavior of the novel A3 isoform during induced maturation of HL60 cells.
Multiple isoenzymes of the Na+,K+-ATPase (alpha, alpha+, and alpha 3) have been identified by molecular cloning (Shull, G. E., J. Greeb, and J. B. Lingrel. 1986. Biochemistry. 25:8125-8132; and Schneider, J. W., R. W. Mercer, and E. J. Benz, Jr. 1987. Clin. Res. 35:585A. [Abstr.]). At least one of these, the alpha 3 chain, represents a novel form for which protein products and enzymatic activities are just beginning to be defined in rodents. We have recently demonstrated that expression of alpha 3 is largely confined to neuromuscular tissues of fetal and adult rats (Schneider, J. W., R. W. Mercer, M. Gilmore-Hebert, M. F. Utset, C. Lai, A. Greene, and E. J. Benz, Jr. 1988. Proc. Natl. Acad. Sci. USA. 85:284-288). We now report that certain human leukemia cell lines including HL60, HEL, and Molt 4 express mRNA for both alpha and alpha 3 isoforms of Na+,K+-ATPase; mRNA was not detected in several other cell lines, including K562 and U937; no cell lines expressed alpha+ mRNA. In uninduced HL60 cells, alpha 3 mRNA comprised 20-30% of total Na+,K+-ATPase mRNA. Furthermore, in HL60 and HEL cells, both alpha and alpha 3 mRNA declined after induction of maturation by DMSO, retinoic acid, or hemin. However, the reduction in alpha 3 mRNA was far more dramatic. alpha 3 mRNA virtually disappeared, but alpha mRNA declined by only approximately 50%. In contrast, when maturation of HL60 cells along the monocyte/macrophage lineage was induced by exposure to phorbol esters, alpha 3 mRNA remained abundant. Moreover, mRNA for the beta subunit of the Na+,K+-ATPase increased dramatically. Our results demonstrate that the alpha 3 isoform, formerly thought to be confined to neuromuscular tissues, is expressed in restricted lineages of hematopoietic origin. These leukemia cell lines should provide a useful model for analyzing regulation of the alpha 3 isoform gene and characterization of alpha 3 isoform activities.
Gilmore-Hebert
M
M
Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06510.
Schneider
J W
JW
Greene
A L
AL
Berliner
N
N
Stolle
C A
CA
Lomax
K
K
Mercer
R W
RW
Benz
E J
EJ
D000818:Animals; D015152:Blotting, Northern; D002460:Cell Line; D004247:DNA; D015342:DNA Probes; D005786:Gene Expression Regulation; D006413:Hematopoietic System / Q000201:enzymology*; D006801:Humans; D007527:Isoenzymes / Q000235:genetics*; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics*
D015342:DNA Probes; D007527:Isoenzymes; D012333:RNA, Messenger; D004247:DNA; D000254:Sodium-Potassium-Exchanging ATPase