A functional P2X7 splice variant with an alternative transmembrane domain 1 escapes gene inactivation in P2X7 knock-out mice.
The ATP-activated P2X7 receptor channel is involved in immune function and inflammatory pain and represents an important drug target. Here we describe a new P2X7 splice variant (P2X7(k)), containing an alternative intracellular N terminus and first transmembrane domain encoded by a novel exon 1 in the rodent P2rx7 gene. Whole cell patch clamp recordings of the rat isoform expressed in HEK293 cells revealed an 8-fold higher sensitivity to the agonist Bz-ATP and much slower deactivation kinetics when compared with the P2X7(a) receptor. Permeability measurements in Xenopus oocytes show a high permeability for N-methyl-D-glucamine immediately upon activation, suggesting that the P2X7(k) channel is constitutively dilated upon opening. The rates of agonist-induced dye uptake and membrane blebbing in HEK cells were also increased. PCR analyses and biochemical analysis by SDS-PAGE and BN-PAGE indicate that the P2X7(k) variant escapes gene deletion in one of the available P2X7(-/-) mice strains and is strongly expressed in the spleen. Taken together, we describe a novel P2X7 isoform with distinct functional properties that contributes to the diversity of P2X7 receptor signaling. Its presence in one of the P2X7(-/-) strains has important implications for our understanding of the role of this receptor in health and disease.
Nicke
Annette
A
Department of Neurochemistry, Max Planck Institute (MPI) for Brain Research, Deutschordenstrasse 46, Frankfurt 60528, Germany. anicke@gwdg.de
Kuan
Yung-Hui
YH
Masin
Marianela
M
Rettinger
Jürgen
J
Marquez-Klaka
Benjamin
B
Bender
Olaf
O
Górecki
Dariusz C
DC
Murrell-Lagnado
Ruth D
RD
Soto
Florentina
F
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D017398:Alternative Splicing / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D005091:Exons / Q000502:physiology; D005971:Glutamates / Q000494:pharmacology; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009865:Oocytes; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014982:Xenopus laevis
D005971:Glutamates; C546468:P2RX7 protein, human; C546469:P2rx7 protein, mouse; C546470:P2rx7 protein, rat; D010975:Platelet Aggregation Inhibitors; D020033:Protein Isoforms; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; C014574:gamma-glutamylmethylamide; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D000255:Adenosine Triphosphate