| Co-Investigator(Kenkyū-buntansha) |
HOSHI Naoto Kanazawa University, Graduate School of Medical Science, Instructor, 大学院・医学系研究科, 助手 (90229170)
HASHII Minako Kanazawa University, Graduate School of Medical Science, Assistant Professor, 大学院・医学系研究科, 講師 (10272957)
YOKOYAMA Shigeru Kanazawa University, Graduate School of Medical Science, Associate Professor, 大学院・医学系研究科, 助教授 (00210633)
|
|---|
| Research Abstract |
We previously reported that stimulation of β-adrenergic and angiotensin II receptors modulates activity of ADP-ribosyl cyclase, a synthetic enzyme of cADP-ribose, and showed that cADP-ribose is a critical molecule in sympathetic potentiation of heart contraction, post-natal heart growth, and neuron-glia interaction. In the present study, we used the same strategy to explore the idea mat cADP-ribose is a second messenger downstream of the mGluRs. We first measured ADP-ribosyl cyclase activity in crude membranes from various rat and mouse nervous tissues in the presence or absence of glutamate and/or GTP. Second, the coupling preference of mGluRs to ADP-ribosyl cyclase was examined in NG108-15 neuroblastoma x glioma hybrid cells over-expressing each subtype.
Glutamate stimulates ADP-ribosyl cyclase activity in rat or mouse crude membranes of retina via group III mGIuRs or in superior cervical ganglion via group I mGluRs. The retina of mGluR6 deficient mice showed no increase in the ADP-ribosyl cyclase level in response to glutamate. GTP enhanced the initial rate of basal and glutamate-stimutated cyclase activity. GTP-γ-S also stimulated basal activity. To determine whether the coupling mode of mGluRs to ADP-ribosyl cyciase is a feature common to individual cloned mGIuRs, we expressed each mGluR subtype in NG108-15 neuroblastoma x glioma hybrid cells. The glutamate-induced stimulation of the cyclase occurs preferentially in NG108-15 cells over-expressing mGluRs1, 3, 5, and 6. Cells expressing mGluR2 or mGluRs4 and 7 exhibit inhibition or no coupling, respectively. Glutamate-induced activation or inhibition of the cyclase activity was eliminated after pretreatment with cholera or pertussis toxin, respectively. Thus, the subtype-specific coupling of mGIuRs to ADP-ribosyl cyclase via G proteins suggests that some glutamate-evoked neuronal function is mediated by cADP-ribose.
|
