Induction of Erythroid Differentiation by Altered G sub( alpha 16) Activity as Detected by a Reporter Gene Assay in MB-02 Cells

• Published in: The Journal of biological chemistry 1999-04, Vol.274 (18), p.12848-12854
• Main Authors: Ghose, S, Porzig, H, Baltensperger, K
• Format: Article
• Language: English
• ISSN: 0021-9258

Heterotrimeric G proteins may assume modulatory roles in cellular proliferation and differentiation. The G protein alpha -subunit G sub( alpha 16), which is specifically expressed in hematopoietic cells, is highly regulated during differentiation of normal and leukemic cells. In human erythroleukemia cells, suppression of G sub( alpha 16) inhibited cellular growth rates. A reporter gene system was established to assess the role of G sub( alpha 16) 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 G sub( alpha 16) led to a significant increase in green fluorescent protein-positive cells, as did transfection with a G sub( alpha 16) antisense plasmid (154 and 156% of controls respectively). The GTPase-deficient, constitutively active mutant of G sub( alpha 16), G sub( alpha 16)R186C, further stimulated differentiation to 195% of control values. Because the effect of G sub( alpha 16) is triggered most efficiently by the GTP-bound protein, an indirect action through interference of overexpressed G sub( alpha 16) with G protein beta gamma -subunits can be excluded. The corresponding mutant of G sub( alpha q) (G sub( alpha q)R182C), the phylogenetically closest family member of G sub( alpha 16), had no effect. The data define a specific role for G sub( alpha 16)-dependent signal transduction in cellular differentiation: deviations from optimal levels of G sub( alpha 16) functional activity lead to reduced growth rates and promote differentiation in hematopoietic cells.