Altered Extracellular Signal-regulated Kinase Signal Transduction by the Muscarinic Acetylcholine and Metabotropic Glutamate Receptors after Cerebral Ischemia

Abstract

To determine whether muscarinic acetylcholine receptors (mAChR) in the post-ischemic hippocampus may be involved in altered extracellular signal-regulated kinases (ERK) signal transduction, we have investigated changes in the activity of ERK1/2 induced by a muscarinic agonist, carbachol. Cerebral ischemia was produced in the rat by injecting 900 microspheres (48 m in diameter) into the right internal carotid artery. Applying carbachol to the contralateral hippocampal slices from ischemic rats increased the phosphorylation of ERK1/2 but did not increase phosphorylation in the ipsilateral hippocampus. Analysis of M 1 mAChR binding showed that there was no significant difference in the number and K d values between the hippocampi from naïve and ischemic rats. Immunoblotting analysis showed no significant difference in the amount of M 1 mAChR in both hemispheres. In contrast to carbachol stimulation, the protein kinase C activator induced an activation of ERK1/2 in the ipsilateral hippocampus. This increase was shown to occur in neurons by immunofluorescence colocalization study. Carbachol-stimulated tyrosine phosphorylation of the G␣ q/11 , inositol 1,4,5-trisphosphate formation, and association of G␣ q/11 with phospholipase C␤1 were attenuated in the ipsilateral hippocampus. We also found that stimulation of group I metabotropic glutamate receptors, which are linked to G␣ q/11 , failed to increase in phosphorylation of ERK1/2 in the ipsilateral hippocampus. These results suggest that failure in receptor-mediated tyrosine phosphorylation of the G␣ q/11 subunit and a defect in receptor-G␣ q/11-effector coupling in the ischemic hippocampus may be involved in alterations of ERK signal transduction.

Chlorpyrifos Induces Delayed Cytotoxicity after Withdrawal in Primary Hippocampal Neurons through Extracellular Signal-Regulated Kinase Inhibition

“…How activation of ERK1/2 comes to cause inhibition is not clear. Since activation of ERK by stimuli needs energy, 36) we speculate that activation of ERK by CPF pretreatment may consume much energy. Upon the termination of long stimulation, there may be no enough energy for activation of ERK, so activation of ERK1/2 turns into inhibition.…”

“…The ERK1/2 activators in the present study were carbacol and NGF. Carbacol, as a cholinergic agonist, can induce activation of ERK1/2, 25,36) while NGF is a member of a family of neurotrophic factors, known to activate ERK1/2 via RTK. 37) Atropine and PD98059 were used as ERK1/2 inhibitors in the present study.…”

Ischemia Impairs the Association Between Connexin 43 and M3 Subtype of Acetylcholine Muscarinic Receptor (M3-mAChR) in Ventricular Myocytes

“…However, the mechanism by which ischemia affects the interaction between M3-mAChR and connexin 43 is not understood. Ischemia has been shown to cause defective coupling between the muscarinic receptor and Gq-proteins in hippocampus [25]. Also, it is well known that anoxia can stimulate mitogenactivated protein kinase (MAPK) such as ERK, P38 and JNK [26,27].…”

Transient ischemia enhances tyrosine phosphorylation and binding of the NMDA receptor to the Src homology 2 domain of phosphatidylinositol 3‐kinase in the rat hippocampus

“…For immunoblotting, SDS‐solubilized samples from the SH2‐binding assay or immunoprecipitates were separated on 8% polyacrylamide gels and transferred to a polyvinylidene difluoride membrane as described (Takagi et al . 2002).…”