AMPA, not NMDA, activates RhoA GTPases and subsequently phosphorylates moesin.
Glutamate induced rapid phosphorylation of moesin, one of ERM family proteins involved in the ligation of membrane to actin cytoskeleton, in rat hippocampal cells (JBC, 277:16576-16584, 2002). However, the identity of glutamate receptor has not been explored. Here we show that a-amino- 3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor is responsible for glutamate-induced RhoA activation and phosphorylation of moesin. Glutamate induced phosphorylation at Thr-558 of moesin was still detectible upon chelation of Ca(2+), suggesting involvement of AMPA receptor instead of N-methyl D-Aspartate (NMDA) receptor in this phosphorylation of moesin. AMPA but not NMDA- induced moesin phosphorylation was independent of Ca(2+). Both AMPA and NMDA but not Kainate induced moesin phosphorylation at similar levels. However, the kinetics of phosphorylation varied greatly between AMPA and NMDA where AMPA treatment rapidly increased phosphomoesin, which reached a maximum at 10 min after treatment and returned to a basal level at 30 min. In contrast, NMDA-induced phosphorylation of moesin reached a maximum at 30 min after treatment and was remained at higher levels at 60 min. A possible involvement of RhoA and its downstream effector, Rho kinase in the AMPA receptor-triggered phosphorylation of moesin was also explored. The kinetics for the glutamate- induced membrane translocation of RhoA was similar to that of moesin phosphorylation induced by AMPA. Moreover, Y-27632, a specific Rho kinase inhibitor, completely blocked AMPA-induced moesin phosphorylation but had no effect on NMDA-induced moesin phosphorylation. These results suggest that glutamate-induced phosphorylation of moesin may be mediated through the AMPA receptor/RhoA/Rho kinase pathway.
Kim
Su-Jin
SJ
Department of Molecular Cell Biology, Sungkyunkwan Univresity School of Medicine, Suwon 440-746, Korea.
Jeon
Songhee
S
Shin
Eun-Young
EY
Kim
Eung-Gook
EG
Park
Joobae
J
Bae
Chang-Dae
CD
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D018690:Excitatory Amino Acid Agonists / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D007608:Kainic Acid / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism*; D016202:N-Methylaspartate / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D018091:Receptors, AMPA / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000378:metabolism*; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
D018690:Excitatory Amino Acid Agonists; D047908:Intracellular Signaling Peptides and Proteins; D008840:Microfilament Proteins; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; C071058:moesin; D018698:Glutamic Acid; D016202:N-Methylaspartate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein; D007608:Kainic Acid; D002118:Calcium