Induction of erythroid differentiation by altered Galpha16 activity as detected by a reporter gene assay in MB-02 cells.
Heterotrimeric G proteins may assume modulatory roles in cellular proliferation and differentiation. The G protein alpha-subunit Galpha16, which is specifically expressed in hematopoietic cells, is highly regulated during differentiation of normal and leukemic cells. In human erythroleukemia cells, suppression of Galpha16 inhibited cellular growth rates. A reporter gene system was established to assess the role of Galpha16 on erythroid differentiation of MB-02 erythroleukemia cells. It is based on transient transfection with a plasmid that expresses green fluorescent protein under the control of the beta-globin promoter. Expression of Galpha16 led to a significant increase in green fluorescent protein-positive cells, as did transfection with a Galpha16 antisense plasmid (154 and 156% of controls, respectively). The GTPase-deficient, constitutively active mutant of Galpha16, Galpha16R186C, further stimulated differentiation to 195% of control values. Because the effect of Galpha16 is triggered most efficiently by the GTP-bound protein, an indirect action through interference of overexpressed Galpha16 with G protein betagamma-subunits can be excluded. The corresponding mutant of Galphaq (GalphaqR182C), the phylogenetically closest family member of Galpha16, had no effect. The data define a specific role for Galpha16-dependent signal transduction in cellular differentiation: deviations from optimal levels of Galpha16 functional activity lead to reduced growth rates and promote differentiation in hematopoietic cells.
Ghose
S
S
Institute of Pharmacology, University of Bern, Postfach 51, Friedbühlstrasse 49, CH-3010 Bern, Switzerland.
Porzig
H
H
Baltensperger
K
K
D000818:Animals; D019556:COS Cells; D002454:Cell Differentiation / Q000235:genetics; D002455:Cell Division; D002460:Cell Line; D015536:Down-Regulation; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D017930:Genes, Reporter; D006801:Humans; D004915:Leukemia, Erythroblastic, Acute / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D016372:RNA, Antisense / Q000494:pharmacology
D016372:RNA, Antisense; D019204:GTP-Binding Proteins