G-PROTEIN SUBUNIT G-ALPHA-16 EXPRESSION IS RESTRICTED TO PROGENITOR B-CELLS DURING HUMAN B-CELL DIFFERENTIATION

Recently G alpha 16, a new guanosine triphosphate (GTP) binding protei n alpha subunit has been described to be specifically expressed in hum an hematopoietic cells. Expression of G alpha 16 was observed in human cell lines of myelomonocytic and T-lymphocytic origin, but not in hum an B-cell lines Raji and IM9. We studied the expression of G alpha 16 in human B cells corresponding to different stages of B-cell different iation by means of reverse transcriptase-polymerase chain reaction (RT -PCR) and Western blotting. The human Burkitt's lymphoma cell lines Ra ji, Ramos, BJAB, the lymphoblastoid cell line SKW6.4, and the plasmocy toma cell line U266 were devoid of G alpha 16. In contrast, G alpha 16 was detected in the human progenitor B cell lines Reh and Nalm-6. Usi ng the mu(+), k(-) cell line BLIN-1 (pre-B cell phenotype) and its der ived subclone 1E8 (surface mu(+), k(+); B-cell phenotype) G alpha 16 e xpression was found to disappear on transition from pre-B to B-cell di fferentiation stage. The analysis of a broad panel of human neoplastic B lymphocytes ranging from progenitor B-acute lymphatic leukemia (pre -pre-B-ALL), common acute leukemias (cALL), pre-B-ALL, mature B-ALL to low grade B-cell lymphoma (chronic lymphocytic leukemia of B-cell typ e, leukemic centrocytic non-Hodgkins lymphoma [NHL], hairy cell leukem ia) showed that G alpha 16 expression is limited to progenitor and pre -B-ALL cells. Therefore, we conclude that within B-cell differentiatio n, G alpha 16 is expressed solely during early B cell ontogeny and dow nregulated during differentiation. Thus, G alpha 16 might be an import ant regulator involved in signaling processes in progenitor B cells. ( C) 1995 by The American Society of Hematology.