(+)-MCPG induces PKCepsilon translocation in cortical synaptosomes through a PLD-coupled mGluR.
We have tested whether different agonists of metabotropic glutamate receptors could induce translocation of selective protein kinase C isozymes in nerve terminals. In rat cortical synaptosomes 1S, 3R-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3R-ACPD; 100 microM) induced an increase in translocation to 124.6 +/- 5.7% of basal unstimulated conditions of the Ca++-independent protein kinase Cepsilon, but not of the Ca++-dependent isozyme beta. This effect was counteracted by 1-aminoindan-1,5-dicarboxylic acid (100 microM), an antagonist of metabotropic glutamate receptor 1. On the other hand, (+)-alpha-methyl-4-carboxyphenylglycine [(+)-MCPG], an antagonist of metabotropic glutamate receptors group I and II, did not antagonize the effect of 1S,3R-ACPD, and per se induced a translocation of protein kinase Cepsilon of 164 +/- 17.7% of basal unstimulated conditions. Because the (+)-MCPG induction of protein kinase Cepsilon translocation was not antagonized by 1-aminoindan-1, 5-dicarboxylic acid, it is suggested that 1S,3R-ACPD and (+)-MCPG activate this signal transduction pathway through distinct membrane receptors. Indeed (2-[2"-carboxy-3'-phenylcyclopropyl]glycine)-13 (300 nM), a new compound known to antagonize metabotropic glutamate receptors coupled to phospholipase D, was able to antagonize protein kinase Cepsilon translocation induced by (+)-MCPG. Moreover (+)-MCPG directly induced phospholipase D activity, measured as [3H]phosphoethanol production in cortical synaptosomes. These data suggest that in cortical nerve terminals (i) distinct metabotropic glutamate receptors, coupled to different signal transduction pathways, are present, (ii) (+)-MCPG is able to induce protein kinase Cepsilon translocation, and that (iii) a metabotropic glutamate receptor associated to phospholipase D might influence translocation of protein kinase C in a calcium-independent manner.
Pastorino
L
L
Institute of Pharmacological Sciences, University of Milano, via Balzaretti 9-20133 Milano, Italy. lucia.pastorino@unimi.it
Colciaghi
F
F
Gardoni
F
F
Albani-Torregrossa
S
S
Pellegrini-Giampietro
D E
DE
Moroni
F
F
De Graan
P N
PN
Cattabeni
F
F
Di Luca
M
M
D000818:Animals; D001565:Benzoates / Q000494:pharmacology*; D002540:Cerebral Cortex / Q000166:cytology; D002614:Chelating Agents / Q000494:pharmacology; D003515:Cycloleucine / Q000031:analogs & derivatives / Q000494:pharmacology; D003521:Cyclopropanes / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism*; D008297:Male; D009474:Neurons / Q000737:chemistry / Q000201:enzymology; D018696:Neuroprotective Agents / Q000494:pharmacology; D010739:Phospholipase D / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000737:chemistry / Q000201:enzymology; D011493:Protein Kinase C / Q000378:metabolism*; D064546:Protein Kinase C beta; D051744:Protein Kinase C-epsilon; D051381:Rats; D017207:Rats, Sprague-Dawley; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013574:Synaptosomes / Q000201:enzymology*
C099854:2-(2'-carboxy-3'-phenylcyclopropyl)glycine; D001565:Benzoates; D002614:Chelating Agents; D003521:Cyclopropanes; D018691:Excitatory Amino Acid Antagonists; D007527:Isoenzymes; D018696:Neuroprotective Agents; D018094:Receptors, Metabotropic Glutamate; D003515:Cycloleucine; C036361:1-amino-1,3-dicarboxycyclopentane; C079694:alpha-methyl-4-carboxyphenylglycine; D004533:Egtazic Acid; C497257:Prkce protein, rat; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D051744:Protein Kinase C-epsilon; D010739:Phospholipase D; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D005998:Glycine