Receptor-linked early events induced by vasoactive intestinal contractor (VIC) on neuroblastoma and vascular smooth-muscle cells

T. Fu, Y. Okano, W. Zhang, T. Ozeki, Y. Mitsui, Y. Nozawa*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

Vasoactive intestinal contractor (VIC) caused a series of biochemical events, including the temporal biphasic accumulation of 1,2-diacylglycerol (DAG), transient formation of Ins(1,4,5)P3, and increase in intracellular free Ca2+ ([Ca2+](i)) in neuroblastoma NG108-15 cells. In these cellular responses, VIC was found to be much more potent in NG108-15 cells than in cultured rat vascular smooth-muscle cells. The single cell [Ca2+](i) assay revealed that in the presence of nifedipine (1 μM) or EGTA (1 mM), the peak [Ca2+](i) declined more rapidly to the resting level in VIC-stimulated NG108-15 cells, indicating that the receptor-mediated intracellular Ca2+ mobilization is followed by Ca2+ influx through the nifedipine-sensitive Ca2+ channel. Pretreatment with pertussis toxin only partially decreased Ins(1,4,5)P3 generation as well as the [Ca2+](i) transient induced by VIC, whereas these events induced by endothelin-1 were not affected by the toxin, suggesting involvement of distinct GTP-binding proteins. The VIC-induced transient Ins(1,4,5)P3 formation coincident with the first early peak of DAG formation suggested that PtdIns(4,5)P2 is a principal source of the first DAG increase. Labelling studies with [3H]myristate, [14C]palmitate and [3H]choline indicated that in neuroblastoma cells phosphatidylcholine (PtdCho) was hydrolysed by a phospholipase C to cause the second sustained DAG increase. Down-regulation of protein kinase C (PKC) by prolonged pretreatment with phorbol ester markedly prevented the VIC-induced delayed DAG accumulation. Furthermore, chelation of intracellular Ca2+ completely abolished the second sustained phase of DAG production. These findings suggest that PtdCho hydrolysis is responsible for the sustained production of DAG and is dependent on both Ca2+ and PKC.

Original languageEnglish (US)
Pages (from-to)71-77
Number of pages7
JournalBiochemical Journal
Volume272
Issue number1
DOIs
StatePublished - 1990

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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