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G alpha 16, a G protein alpha subunit specifically expressed in hematopoietic cells
T T Amatruda1, D A Steele, V Z Slepak
1Division of Biology 147-75, California Institute of Technology, Pasadena 91125.
Summary
A novel G protein alpha subunit, G alpha 16, is specifically found in hematopoietic cells. Its unique structure suggests it regulates cell-specific signaling pathways not affected by pertussis toxin.
Area of Science:
- Molecular Biology
- Cell Biology
- Immunology
Background:
- Guanine nucleotide-binding regulatory proteins (G proteins) mediate critical signal-transduction pathways in hematopoietic cells.
- A specific G protein alpha subunit gene, G alpha 16, has been identified and is expressed in human hematopoietic cells.
Purpose of the Study:
- To characterize the novel G alpha 16 gene and its protein product.
- To investigate the expression pattern and potential function of G alpha 16 in hematopoietic cells.
Main Methods:
- cDNA sequencing and protein prediction for G alpha 16.
- Gene expression analysis in various cell lines (myelomonocytic, T-cell, B-cell, non-hematopoietic).
- Western blot analysis using specific antisera against G alpha 16.
Main Results:
- G alpha 16 encodes a protein resembling the Gq class, lacking a pertussis toxin site, with distinct sequence features.
- G alpha 16 is expressed in myelomonocytic and T-cell lines but not in B-cell or non-hematopoietic lines.
- Expression is downregulated upon differentiation of HL-60 cells; the corresponding protein is detected in HL-60 membranes.
Conclusions:
- G alpha 16 is a hematopoietic-specific G protein alpha subunit.
- Its restricted expression suggests a role in cell-type-specific signal transduction.
- G alpha 16 mediates pathways independent of pertussis toxin inhibition.