Possible role of Ca2+-independent protein kinase C isozyme, nPKCɛ, in thyrotropin- releasing hormone-stimulated signal transduction: Differential down-regulation of nPKCɛ in GH4C1 cells

doi:10.1016/S0006-291X(05)80191-3

Biochemical and Biophysical Research Communications

Volume 172, Issue 1, 15 October 1990, Pages 184-189

https://doi.org/10.1016/S0006-291X(05)80191-3 Get rights and content

Abstract

Protein kinase C (PKC) molecular species of GH₄C₁ cells were analyzed after separation by hydroxyapatite column chromatography. A novel Ca²⁺-independent PKC, nPKC ɛ, was identified together with two conventional Ca²⁺-dependent PKCs, PKCα and βII by analysis of kinase and phorbol ester-binding activities, immunoblotting using isozyme-specific antibodies, and Northern blotting. These PKCs are down-regulated differently when cells are stimulated by outer stimuli; phorbol esters deplete PKCβII and nPKC ɛ from the cells more rapidly than PKC α, whereas thyrotropin-releasing hormone (TRH) at 200 nM depletes nPKCɛ exclusively with a time course similar to that induced by phorbol esters. However, translocation of PKCα and βII to the membranes is elicited by both TRH and phorbol esters. These results suggest that TRH and phorbol ester activate PKC α and βII differently but that nPKC ɛ is stimulated similarly by both stimuli. Thus, in GH₄C₁ cells, Ca²⁺-independent nPKC ɛ may play a crucial role distinct from that mediated by Ca²⁺-dependent PKC α and βII in a cellular response elicited by both TRH and phorbol esters.

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^*: Supported in part by research grants from the Ministry of Education, Science, and Culture of Japan.

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Possible role of Ca2+-independent protein kinase C isozyme, nPKCɛ, in thyrotropin- releasing hormone-stimulated signal transduction: Differential down-regulation of nPKCɛ in GH4C1 cells*

Abstract

Cell

Cell

J. Biol. Chem.

Biochem. Biophys. Res. Commun.

FEBS Lett.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

Methods Enzymol.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

Possible role of Ca²⁺-independent protein kinase C isozyme, nPKCɛ, in thyrotropin- releasing hormone-stimulated signal transduction: Differential down-regulation of nPKCɛ in GH₄C₁ cells*