Involvement of Protein Kinase C in γ‐Aminobutyric Acid Release from Xenopus Oocytes Injected with Rat Brain mRNA

Abstract

Involvement of protein kinase C (PKC) in the release of y-aminobutyric acid (GABA) was examined in Xenopus IaevIs oocytes injected with mRNA from rat cerebellum, as compared with findings in slices of rat cerebellum. The mRNA-injected 00cytes preloaded with [ 3H}GABA showed spontaneous release of [3H]GABA,~-0.5% of GABA content per 1 mm. Stimulation with either Ca2 ionophore (A231 87) or a high~concentration increased the release of [3H]GABA from slices of rat deep cerebellar nucleus and mRNA-injected oocytes but not from noninjected and water-injected oocytes. 12-O-Tetradecanoylphorbol 13-acetate (10-300 nM) but not 4a-phorbol 12,13-didecanoate (300 nM) potentiated the A23187-stimulated release of [3Hj-GABA from slices and from mRNA-injected oocytes, in a concentration-dependent manner. Thus, machinery associated with release processes of GABA can be expressed in oocytes by injecting rat cerebellar mRNA, and PKC participates in GABA release from the functionally expressed GABAergic nerve terminals. Key Words: y-Aminobutyric acid release-Protein kinase C-Cerebellum -Xenopus oocyte-Rat cerebellar mRNA-1 2-O-Tetradecanoylphorbol 1 3-acetate-4a-Phorbol 12,1 3-didecanoate.J. Neurochem. 67, 868-871 (1996).The release of neurotransmitter, in particular acetylcholine, has been examined in the electric organ of•~~()rped() ularrnorata (Dunant and Israel, I 985 ) and the giant synapse of the squid Loligo pealei (Bommert et al., 1993; Hunt ci al., 1994). The nerve terminals in mammalian tissues are too minute in size to examine precisely mechanisms related to neurotransmitter release; therefore, cells such as COS and chromaffin cells, Drosophila, and yeast are used as substi-tute~for nerve terminals (Shoji-Kasal et al., 1992;Bennett et al., 1993;Protopopov et al., 1993; DiAntonio and Schwarz, 1994). Xenopus laevis oocytes injected with mRNA or After washing in fresh solution for 60 mm, each slice was Resubmitted manuscriptAbbreviations used: aPKC, atypical protein kinase C; cPKC, classical protein kinase C; GABA, y-aminohutyric acid; nPKC, novel protemi kinasc C; 4o-PDD, 4a-phorhol 12,13-didecanoate; PKC, protein kinasc C; TPA, 12-O-tetradecanoylphorhol 13-acetate.

Presynaptic Modulation of Cholecystokinin Release by Protein Kinase C in the Rat Hippocampus

“…results in longer duration of 4-APinduced repetitive action potentials, Ca2" entry (built up of the bulk [Ca2"] 1), and glutamate exocytosis (Tibbs et al, 1989(Tibbs et al, , 1996. Such a mechanism could also be effective for slow CCK-8 and fast GABA exocytosis, in contrast with other studies using KC1 depolarization (Allard and Beinfeld, 1988;Shuntoh et al, 1989;Kan et al, 1996). Although the locus of action of PKC may be quite similar for stimulating both CCK-8 and GABA exocytosis, the two transmitters showed a difference in their sensitivity for /3-PDBu (Fig.…”

“…One of the enzymes involved in modulating the release of SCCV containing the transmitter glutamate is protein kinase C (PKC), although the locus of its action is still controversial (Nichols et al, 1987;Barrie et al, 1991;Terrian et al, 1991;Sanchez-Prieto et al, 1994). It was observed that PKC also stimulates vesicular GABA release in several cellular preparations (Shuntoh et al, 1989;Kan et al, 1996), but it has not yet been shown in isolated synaptosomes. PKC is a Ca2t and phospholipid-dependent enzyme Cholecystokinin (CCK)-like immunoreactivity (CCK-LI) has been detected throughout the CNS but is particularly abundant in the neocortex and the hippocampus (Innis et al, 1979).…”