Agonist‐Induced, GTP‐Dependent Phosphoinositide Hydrolysis in Postmortem Human Brain Membranes

Richard S. Jope, Ling Song, Richard Powers

Research output: Contribution to journalArticle

29 Scopus citations

Abstract

Membranes prepared from postmortem human brain were used to measure the activities of three components of the phosphoinositide second messenger system. [3H]Phosphatidylinositol ([3H]PI) hydrolysis was stimulated by directly activating phospholipase C with calcium, by activating guanine nucleotide-binding proteins (G proteins) with guanosine-5′-O-(3-thiotriphosphate) (GTPγS) or with AIF4, and by receptors activated with several agonists (in the presence of GTPγS), including (in order of increasing magnitudes of responses) carbachol, pilocarpine, histamine, trans-1-aminocyclopentyl-1,3-dicarboxylic acid (a selective excitatory amino acid metabotropic receptor agonist), serotonin, and ATP. Gq/11 was identified as the G protein most likely to mediate [3H]PI hydrolysis in human brain membranes based on the findings that this process was not impaired by pretreatment with pertussis toxin and it was inhibited by antibodies specific for the α-subunit of Gq/11 but not by antibodies for Go or Gi1. The effects of postmortem delay on [3H]PI hydrolysis were examined by studying tissues obtained 6-21 h postmortem. A slight increase in basal [3H]PI hydrolysis was associated with increased postmortem time, suggesting a slow loss of the normal inhibitory control of phospholipase C. GTPγS-stimulated [3H]PI hydrolysis was unaffected by postmortem times within this range, but carbachol-induced [3H]PI hydrolysis tended to decrease with increasing postmortem times. These results demonstrate that the entire phosphoinositide complex remains functional and experimentally detectable in postmortem human brain membranes. This method provides a means to study the function, regulation, effects of diseases, and responses to drugs of the phosphoinositide system in human brain.

Original languageEnglish (US)
Pages (from-to)180-186
Number of pages7
JournalJournal of neurochemistry
Volume62
Issue number1
DOIs
StatePublished - Jan 1994
Externally publishedYes

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Keywords

  • G protein
  • Human brain
  • Phosphatidylinositol hydrolysis
  • Phosphoinositide
  • Phospholipase c

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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