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Dopamine Release via Protein Kinase C Activation in the Fish Retina
Author(s) -
Kato S.,
Ishita S.,
Mawatari K,
Matsukawa T.,
Negishi K.
Publication year - 1990
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1990.tb04914.x
Subject(s) - protein kinase c , diacylglycerol kinase , microbiology and biotechnology , activator (genetics) , protein kinase a , carp , phorbol , endogeny , biology , retina , dopamine , chemistry , biochemistry , phosphorylation , endocrinology , receptor , fish <actinopterygii> , neuroscience , fishery
Calcium‐dependent phospholipid‐sensitive protein kinase [protein kinase C (PKC)] was partially purified from the carp ( Cyprinus carpio ) retina through DE 52 ion exchange and Cellulofine gel filtration chromatography. The phorbol ester 12‐ O ‐tetradecanoylphorbol 13‐acetate (TPA) activated PKC in the nanomolar range. A major 38‐kDa protein in the retinal supernatants (105,000 g ) was phosphorylated in vitro by PKC during a short period (3 min). Other phosphoproteins also appeared during a further prolonged period (>15 min). Rod‐bipolar and dopamine (DA) interplexiform cells in the fish retina were immunoreactive to a monoclonal antibody to PKC (α/β‐subtype). The PKC antibody recognized a 78‐kDa native PKC enzyme by means of an immunoblotting method. Subsequently, the effects of two kinds of PKC activators were investigated on [ 3 H]DA release from retinal cell fractions containing DA cells that had been preloaded with [ 3 H]DA. A phorbol ester (TPA) induced a calcium‐ and dose‐dependent [ 3 H]DA release during a short period (2 min), with the minimal effective dose being 1 n M . Other phorbols having no tumor‐promoting activity, such as 4β‐phorbol and 4α‐phorbol 12, 13‐didecanoate, were ineffective on [ 3 H]DA release. A synthetic diacylglycerol [1‐oleoyl‐2‐acetylglycerol (OAG)], which is an endogenous PKC activator, was also able to induce a significant release of [ 3 H]DA. Furthermore, TPA was found to release endogenous DA from isolated fish retina by a highly sensitive HPLC with electrochemical detection method. The OAG‐ or TPA‐induced [ 3 H]DA or DA release was completely blocked by inhibitors of PKC, such as 1‐(5‐isoquinolinesulfonyl)‐2‐methylpiperazine (H 7 ) and staurosporine. In contrast, release of [ 3 H]glycine, γ‐[ 3 H]aminobutyric acid, and D‐[ 3 H]aspartic acid was never induced by TPA. Taken together, the present data indicate that TPA or OAG triggers a release of DA synaptically and that the induction is due to a PKC activation specifically in the membrane of DA cells in the fish retina. The functional role of PKC in rod‐bipolar cells is unknown at present.