Spatial-temporal patterning of metabotropic glutamate receptor-mediated inositol 1,4,5-triphosphate, calcium, and protein kinase C oscillations - Protein kinase C-dependent receptor phosphorylation is not required

John P. Robarts Research Institute, P. O. Box 5015, 100 Perth Drive, London, Ontario N6A 5K8, Canada.
Journal of Biological Chemistry (Impact Factor: 4.57). 10/2001; 276(38):35900-8. DOI: 10.1074/jbc.M103847200
Source: PubMed


The metabotropic glutamate receptors (mGluR), mGluR1a and mGluR5a, are G protein-coupled receptors that couple via Gq to the hydrolysis of phosphoinositides, the release of Ca2+ from intracellular stores, and the activation of protein kinase C (PKC). We show here that mGluR1/5 activation results in
oscillatory G protein coupling to phospholipase C thereby stimulating oscillations in both inositol 1,4,5-triphosphate formation
and intracellular Ca2+ concentrations. The mGluR1/5-stimulated Ca2+ oscillations are translated into the synchronized repetitive redistribution of PKCβII between the cytosol and plasma membrane.
The frequency at which mGluR1a and mGluR5a subtypes stimulate inositol 1,4,5-triphosphate, Ca2+, and PKCβII oscillations is regulated by the charge of a single amino acid residue localized within their G protein-coupling
domains. However, oscillatory mGluR signaling does not involve the repetitive feedback phosphorylation and desensitization
of mGluR activity, since mutation of the putative PKC consensus sites within the first and second intracellular loops as well
as the carboxyl-terminal tail does not prevent mGluR1a-stimulated PKCβII oscillations. Furthermore, oscillations in Ca2+ continued in the presence of PKC inhibitors, which blocked PKCβII redistribution from the plasma membrane back into the cytosol.
We conclude that oscillatory mGluR signaling represents an intrinsic receptor/G protein coupling property that does not involve
PKC feedback phosphorylation.

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    • "Human embryonic kidney (HEK) 293 cells were maintained in Eagle's minimal essential medium supplemented with 8% (v/v) heat inactivated fetal bovine serum and 50 mg/ml of gentamicin. Cells seeded in 100-mm dishes were transfected using a modified calcium phosphate method as described previously (Dale et al., 2001). After transfection (18 hours), the cells were incubated with fresh medium and allowed to recover for 24 hours for coimmunoprecipitation studies. "
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    • "eptor phosphorylation , specifi - cally at Ser 839 , to uncouple the receptor from Gq / 11 and an as yet poorly defined protein phosphatase activity rapidly dephosphorylates the receptor to allow restoration of mGlu5 receptor – Gq / 11 coupling ( Kawabata et al . , 1996 ; Nakahara et al . , 1997 ; Nash et al . , 2002 ; Kim et al . , 2005 ; but see Dale et al . , 2001 ) . Stimulation of the astrocyte mGlu5 receptor initiates robust Ca 2+ oscillations that can reach a frequency of approxi - mately three oscillations per minute . Application of calyculin A or cantharidin , relatively selective inhibitors of the serine / threonine protein phosphatases PP1 / PP2A ( Ishihara et al . , 1989 ; Honkanen , 19"
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