G protein subunit G gamma 13 is coexpressed with G alpha o, G beta 3, and G beta 4 in retinal ON bipolar cells.
We investigated the expression of Ggamma13, a recently discovered G protein subunit, and a selection of Gbeta subunits in retinal bipolar cells, by using a transgenic mouse strain in which green fluorescent protein is strongly expressed in a single type of cone bipolar cell. The cells have ON morphology, and patch-clamp recordings in slices confirmed that they are of the physiological ON type. Immunohistochemistry showed that Ggamma13 is expressed in rod bipolar cells and ON cone bipolar cells, where it is colocalized in the dendrites with Galphaomicron. ON and OFF cone bipolar cells and rod bipolar cells were identified among dissociated cells by their green fluorescence and/or distinct morphology. Hybridization of single-cell polymerase chain reaction products with cDNA probes for G protein subunits Gbeta1 to 5 showed that Gbeta3, Gbeta4, and Ggamma13 are coexpressed in ON bipolar cells but not present in OFF bipolar cells. Gbeta1, 2, and 5 are expressed in partially overlapping subpopulations of cone bipolar cells. Ggamma13 and Gbeta3 and/or Gbeta4, thus, seem selectively to participate in signal transduction by ON bipolar cells.
Huang
Liquan
L
Department of Physiology and Biophysics, Mount Sinai School of Medicine, New York, New York 10029, USA.
Max
Marianna
M
Margolskee
Robert F
RF
Su
Hui
H
Masland
Richard H
RH
Euler
Thomas
T
D000818:Animals; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D005786:Gene Expression Regulation / Q000502:physiology; D020962:Heterotrimeric GTP-Binding Proteins / Q000096:biosynthesis*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D021122:Protein Subunits / Q000096:biosynthesis*; D012160:Retina / Q000737:chemistry / Q000378:metabolism*; D017949:Retinal Cone Photoreceptor Cells / Q000737:chemistry / Q000378:metabolism; D017948:Retinal Rod Photoreceptor Cells / Q000737:chemistry / Q000378:metabolism
C454420:G-protein beta3 subunit; D021122:Protein Subunits; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020962:Heterotrimeric GTP-Binding Proteins