EXPRESSION OF 2 INWARD RECTIFIER POTASSIUM CHANNELS IS ESSENTIAL FOR DIFFERENTIATION OF PRIMITIVE HUMAN HEMATOPOIETIC PROGENITOR CELLS

A potassium inward rectifier (K-ir) current was previously shown by us to be induced in primitive hematopoietic progenitor cells, stimulated with the combination of interleukin-3 (IL-3) and stem cell factor (SC F). Biophysical features of whole cell currents implicated the involve ment of more than one K-ir channel type. Employing IL-3 + SCF stimulat ed human cord blood CD34(+)38(-) cells, we isolated and characterized different components of this current. Reverse transcription-polymerase chain reaction (RT-PCR) subcloning identified the expression of a str ongly rectifying K-ir channel (K-ir 4.3) as well as a weakly rectifyin g K-ir channel (K-ir 1.1) in these cells. Inhibition of the expression of each of the channels suppressed progenitor cell generation by IL-3 and SCF-stimulated CD34(+)38(-) cells in 7-day suspension cultures. T he variable expression of two essential inward rectifying potassium ch annels early in the course of hematopoietic progenitor cell differenti ation may play a potentially important role in potassium homeostasis i n these cells. I. Cell. Physiol. 177:197-205, 1998. (C) 1998 Wiley-Lis s Inc.