Back to Search
Start Over
The luteinizing hormone receptor activates phospholipase C via preferential coupling to Gi2.
- Source :
-
Biochemistry [Biochemistry] 1999 Sep 21; Vol. 38 (38), pp. 12490-8. - Publication Year :
- 1999
-
Abstract
- Binding of lutropin/choriogonadotropin (LH/CG) to its cognate receptor results in the activation of adenylyl cyclase and phospholipase C. This divergent signaling of the LH receptor is based on the independent activation of distinct G protein subfamilies, i.e. , Gs, Gi, and potentially also Gq. To examine the selectivity of LH receptor coupling to phospholipase C beta-activating G proteins, we used an in vivo reconstitution system based on the coexpression of the LH receptor and different G proteins in baculovirus-infected insect cells. In this paper, we describe a refined expression strategy for the LH receptor in insect cells. The receptor protein was inserted into the cell membrane at an expression level of 0.8 pmol/mg of membrane protein. Sf9 cells expressing the LH receptor responded to hCG challenge with a concentration-dependent accumulation of intracellular cAMP (EC50 = 630 nM) but not of inositol phosphates, whereas stimulation of the histamine H1 receptor in Sf9 cells led to increased phospholipase C (PLC) activity. Immunoblotting experiments using G protein-specific antisera revealed the absence of quantitative amounts of alpha i in Sf9 cells, whereas alpha s and alpha q/11 were detected. We therefore attempted to restore the hCG-dependent PLC activation by infection of Sf9 cells with viruses encoding the LH receptor and different G protein alpha subunits. HCG stimulation of cells coexpressing the LH receptor and exogenous alpha i2 resulted in stimulation of PLC activity. In cells coinfected with an alpha i3-baculovirus, hCG challenge led to a minor activation of PLC, whereas no hCG-dependent PLC stimulation was observed in cells coexpressing alpha i1. Most notably, coinfection with baculoviruses encoding alpha q or alpha 11 did not reproduce the PLC activation by the LH receptor. Thus, the murine LH receptor activates adenylyl cyclase via Gs and PLC via selective coupling to Gi2.
- Subjects :
- Animals
Baculoviridae genetics
Cells, Cultured
Chorionic Gonadotropin metabolism
Chorionic Gonadotropin physiology
Cyclic AMP metabolism
Enzyme Activation genetics
GTP-Binding Protein alpha Subunit, Gi2
Genetic Vectors metabolism
Guinea Pigs
Heterotrimeric GTP-Binding Proteins biosynthesis
Heterotrimeric GTP-Binding Proteins genetics
Inositol Phosphates metabolism
Iodine Radioisotopes
Mice
Protein Binding genetics
Proto-Oncogene Proteins biosynthesis
Proto-Oncogene Proteins genetics
Receptors, LH genetics
Receptors, LH metabolism
Recombinant Proteins genetics
Recombinant Proteins metabolism
Spodoptera genetics
Type C Phospholipases genetics
GTP-Binding Protein alpha Subunits, Gi-Go
Heterotrimeric GTP-Binding Proteins metabolism
Proto-Oncogene Proteins metabolism
Receptors, LH physiology
Type C Phospholipases metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0006-2960
- Volume :
- 38
- Issue :
- 38
- Database :
- MEDLINE
- Journal :
- Biochemistry
- Publication Type :
- Academic Journal
- Accession number :
- 10493819
- Full Text :
- https://doi.org/10.1021/bi990755m