The regulation of the cGMP-binding cGMP phosphodiesterase by proteins that are immunologically related to gamma subunit of the photoreceptor cGMP phosphodiesterase

A Lochhead, E Nekrasova, V Y Arshavsky, N J Pyne

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Abstract

The cGMP phosphodiesterase from retinal rods (PDE-6) is an alphabetagamma2 heterotetramer. The alpha and beta subunits contain catalytic sites for cGMP hydrolysis, whereas the gamma subunits serve as a protein inhibitor of the enzyme. Visual excitation of photoreceptors enables the activated GTP-bound form of the G-protein transducin to remove the inhibitory action of the gamma subunit, thereby triggering PDE-6 activation. The type 5 phosphodiesterase (PDE-5) isoform shares a number of similar characteristics with PDE-6, including binding of cGMP to noncatalytic sites, the cyclic nucleotide specificity, and inhibitor sensitivities. Although the functional role of PDE-5 remains unclear, it has been shown to be activated by protein kinase A (PKA) (Burns, F., Rodger, I. W. & Pyne, N. J. (1992) Biochem. J. 283, 487-491). Here we report that both the recombinant gamma subunit and a peptide corresponding to amino acids 24-46 in this protein inhibited the activation of PDE-5 by PKA. Furthermore, immunoblotting airway smooth muscle membranes with a specific antibody against amino acids 24-46 of the PDE-6 gamma subunit identified two major immunoreactive small molecular mass proteins of 14 and 18 kDa (p14 and p18). These appear to form a complex with PDE-5, because PDE activity was immunoprecipitated using antibody against the PDE-6 gamma subunit. p14 and p18 were also substrates for phosphorylation by a unidentified kinase that was stimulated by a pertussis toxin-sensitive G-protein. Phosphorylation of p14/p18 in membranes treated with guanine nucleotides correlated with a concurrent reduction in the activation of PDE-5 by PKA. We suggest that p14 and p18 share an epitope common to PDE-6 gamma and that this region may interact with PDE-5 to prevent its activation by PKA.
Original languageEnglish
Pages (from-to)18397-18403
Number of pages7
JournalJournal of Biological Chemistry
Volume272
Issue number29
DOIs
Publication statusPublished - 18 Jul 1997

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Keywords

  • 3',5'-cyclic-GMP phosphodiesterases
  • adenosine triphosphate
  • animals
  • antibodies
  • binding sites
  • cell membrane
  • cells, cultured
  • cyclic AMP-dependent protein kinases
  • cyclic GMP
  • cyclic nucleotide phosphodiesterases, type 5
  • GTP-binding proteins
  • guanylyl imidodiphosphate
  • guinea pigs
  • homeostasis
  • kinetics
  • lung
  • macromolecular substances
  • muscle, smooth
  • pertussis toxin
  • phosphoric diester hydrolases
  • recombinant proteins
  • retinal rod photoreceptor cells
  • trachea
  • virulence factors, bordetella

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