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Gene Review

PHF5A  -  PHD finger protein 5A

Homo sapiens

Synonyms: INI, MGC1346, PHD finger-like domain protein 5A, PHD finger-like domain-containing protein 5A, Rds3, ...
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High impact information on PHF5A

  • Competition binding experiments revealed a guanine nucleotide-sensitive serotonin high affinity state only for the 5-HT2C-INI receptor; the loss of high affinity agonist binding to the edited receptor demonstrates that RNA editing generates unique 5-HT2CRs that couple less efficiently to G proteins [1].
  • Agonist-stimulated calcium release was examined in NIH-3T3 fibroblasts stably expressing the nonedited human INI (hINI) or the edited hVSV or hVGV variants [2].
  • In contrast, while lacking agonist activity at the VNI and VSV, olanzapine showed inverse agonism at the INI isoform (IC50 594 nM), reaching a maximal attenuation of 20% [3].
  • In human embryonic kidney (HEK) cells transiently expressing 5-HT2C receptor isoforms, aripiprazole exhibited full agonism at the unedited INI, but partial agonism at the partially edited VNI and fully edited VSV isoforms (EC50s of 571, 1086 and 2099 nM, respectively) [3].
  • A 2-hr exposure to 5-HT resulted in a significantly larger reduction in response upon re-exposure to 5-HT at 5-HT(2C (INI)) receptors, as compared to 5-HT(2C (VSV)) receptors (72% and 47% respectively, P < 0.01) [4].

Biological context of PHF5A

  • Saturation analysis using [3H]5-HT revealed high and low affinity recognition sites on the INI isoform in both cell types whilst the VSV isoform did not have the high affinity binding site for [3H]5-HT [5].

Anatomical context of PHF5A

  • As demonstrated by fura2-detection, S16924 concentration-dependently abolished (pKb=7.93) the 5HT-induced elevation in intracellular levels of Ca2+ ([Ca2+]i) in a CHO cell line stably expressing the INI isoform of 5-HT2c receptors [6].

Associations of PHF5A with chemical compounds

  • Additionally, several drugs without significant antipsychotic actions (M100907, ketanserin, mianserin, ritanserin, and amitriptyline) were potent inverse agonists at the 5-HT2C-INI isoform expressed in HEK-293 cells [7].

Analytical, diagnostic and therapeutic context of PHF5A

  • The desensitization characteristics of recombinant human 5-HT(2A), 5-HT(2B), and 5-HT(2C) receptors (VSV and INI isoforms) stably expressed in CHO-K1 (Chinese hamster ovary) cells was investigated by calcium fluorimetry [4].


  1. RNA editing of the human serotonin 5-hydroxytryptamine 2C receptor silences constitutive activity. Niswender, C.M., Copeland, S.C., Herrick-Davis, K., Emeson, R.B., Sanders-Bush, E. J. Biol. Chem. (1999) [Pubmed]
  2. RNA editing of the human serotonin 5-HT(2C) receptor delays agonist-stimulated calcium release. Price, R.D., Sanders-Bush, E. Mol. Pharmacol. (2000) [Pubmed]
  3. Distinct functional profiles of aripiprazole and olanzapine at RNA edited human 5-HT2C receptor isoforms. Zhang, J.Y., Kowal, D.M., Nawoschik, S.P., Lou, Z., Dunlop, J. Biochem. Pharmacol. (2006) [Pubmed]
  4. Agonist-induced functional desensitization of recombinant human 5-HT2 receptors expressed in CHO-K1 cells. Porter, R.H., Malcolm, C.S., Allen, N.H., Lamb, H., Revell, D.F., Sheardown, M.J. Biochem. Pharmacol. (2001) [Pubmed]
  5. Characterisation of agonist binding on human 5-HT2C receptor isoforms. Quirk, K., Lawrence, A., Jones, J., Misra, A., Harvey, V., Lamb, H., Revell, D., Porter, R.H., Knight, A.R. Eur. J. Pharmacol. (2001) [Pubmed]
  6. Antagonist properties of the novel antipsychotic, S16924, at cloned, human serotonin 5-HT2C receptors: a parallel phosphatidylinositol and calcium accumulation comparison with clozapine and haloperidol. Cussac, D., Newman-Tancredi, A., Nicolas, J.P., Boutin, J.A., Millan, M.J. Naunyn Schmiedebergs Arch. Pharmacol. (2000) [Pubmed]
  7. Inverse agonist actions of typical and atypical antipsychotic drugs at the human 5-hydroxytryptamine(2C) receptor. Rauser, L., Savage, J.E., Meltzer, H.Y., Roth, B.L. J. Pharmacol. Exp. Ther. (2001) [Pubmed]
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