Identification of an integration center for cross-talk between protein kinase C and G protein modulation of N-type calcium channels

Citation
J. Hamid et al., Identification of an integration center for cross-talk between protein kinase C and G protein modulation of N-type calcium channels, J BIOL CHEM, 274(10), 1999, pp. 6195-6202
Citations number
40
Categorie Soggetti
Biochemistry & Biophysics
Journal title
JOURNAL OF BIOLOGICAL CHEMISTRY
ISSN journal
00219258 → ACNP
Volume
274
Issue
10
Year of publication
1999
Pages
6195 - 6202
Database
ISI
SICI code
0021-9258(19990305)274:10<6195:IOAICF>2.0.ZU;2-1
Abstract
The modulation of presynaptic calcium channel activity by second messengers provides a fine tuning mechanism for neurotransmitter release. In neurons, the activation of certain G protein-coupled receptors reduces N-type chann el activity by similar to 60%. In contrast, activation of protein kinase C (PKC) results in an approximately 50% increase in N-type channel activity, and subsequent G protein inhibition is antagonized. Here, we describe the m olecular determinants that control the dual effects of PKC-dependent phosph orylation. The double substitution of two adjacent PKC consensus sites in t he calcium channel domain I-II linker (Thr(422), Ser(425)) to alanines abol ished both PKC-dependent up-regulation and the PKC-G protein cross-talk. Th e single substitution of Ser(425) to glutamic acid abolished PRC up-regulat ion but had no effect on G protein modulation. Replacement of Thr(422) With glutamic acid eliminated PKC-dependent up-regulation and mimicked the effe cts of PKC phosphorylation on G protein inhibition. Our data suggest that T hr(422) mediates the antagonistic effect of PKC on G protein modulation, wh ile phosphorylation of either Thr(422) or Ser(425) are sufficient to increa se N-type channel activity. Thus, Thr(422) serves as a molecular switch by which PKC is able to simultaneously trigger the upregulation of channel act ivity and antagonize G protein inhibition.