Functional differences between ATP-gated human and rat P2X3 receptors are caused by critical residues of the intracellular C-terminal domain.
ATP-activated P2X3 receptors of sensory ganglion neurons contribute to pain transduction and are involved in chronic pain signaling. Although highly homologous (97%) in rat and human species, it is unclear whether P2X3 receptors have identical function. Studying human and rat P2X3 receptors expressed in patch-clamped human embryonic kidney (HEK) cells, we investigated the role of non-conserved tyrosine residues in the C-terminal domain (rat tyrosine-393 and human tyrosine-376) as key determinants of receptor function. In comparison with rat P2X3 receptors, human P2X3 receptors were more expressed and produced larger responses with slower desensitization and faster recovery. In general, desensitization was closely related to peak current amplitude for rat and human receptors. Downsizing human receptor expression to the same level of the rat one still yielded larger responses retaining slower desensitization and faster recovery. Mutating phenylalanine-376 into tyrosine in the rat receptor did not change current amplitude; yet, it retarded desensitization onset, demonstrating how this residue was important to functionally link these two receptor states. Conversely, removing tyrosine from position 376 strongly down-regulated human receptor function. The different topology of tyrosine residues in the C-terminal domain has contrasting functional consequences and is sufficient to account for species-specific properties of this pain-transducing channel.
Neuroscience Department and Italian Institute of Technology Unit, International School for Advanced Studies-SISSA, Trieste, Italy.
Mayya
M
Sundukova
Sandra
S
Vilotti
Rita
R
Abbate
Elsa
E
Fabbretti
Andrea
A
Nistri
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D055592:Biophysical Phenomena / Q000187:drug effects / Q000235:genetics; D019921:Biotinylation; D000081247:CSK Tyrosine-Protein Kinase; D004558:Electric Stimulation; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D047468:Immunoprecipitation; D015640:Ion Channel Gating / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D016296:Mutagenesis / Q000502:physiology; D009154:Mutation / Q000235:genetics; D018408:Patch-Clamp Techniques; D010649:Phenylalanine / Q000235:genetics; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D058911:Purinergic P2X Receptor Agonists / Q000494:pharmacology; D034622:RNA Interference / Q000502:physiology; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D058477:Receptors, Purinergic P2X3 / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D013045:Species Specificity; D014162:Transfection; D014443:Tyrosine / Q000235:genetics; D019061:src-Family Kinases
D058911:Purinergic P2X Receptor Agonists; D034741:RNA, Small Interfering; D058477:Receptors, Purinergic P2X3; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D014443:Tyrosine; D010649:Phenylalanine; D000255:Adenosine Triphosphate; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human; C002630:alpha,beta-methyleneadenosine 5'-triphosphate