| Literature References | 1. ATTWOOD, T.K. AND FINDLAY, J.B.C.
Fingerprinting G protein-coupled receptors.
PROTEIN ENG. 7(2) 195-203 (1994).
2. ATTWOOD, T.K. AND FINDLAY, J.B.C.
G protein-coupled receptor fingerprints.
7TM, VOLUME 2, EDS. G.VRIEND AND B.BYWATER (1993).
3. BIRNBAUMER, L.
G proteins in signal transduction.
ANNU.REV.PHARMACOL.TOXICOL. 30 675-705 (1990).
4. CASEY, P.J. AND GILMAN, A.G.
G protein involvement in receptor-effector coupling.
J.BIOL.CHEM. 263(6) 2577-2580 (1988).
5. ATTWOOD, T.K. AND FINDLAY, J.B.C.
Design of a discriminating fingerprint for G protein-coupled receptors.
PROTEIN ENG. 6(2) 167-176 (1993).
6. WATSON, S. AND ARKINSTALL, S.
Adenosine and adenine nucleotides.
IN THE G PROTEIN-LINKED RECEPTOR FACTSBOOK, ACADEMIC PRESS, 1994, PP.19-31.
7. COMMUNI, D., JANSSENS, R., SUAREZ-HUERTA, N., ROBAYE, B. AND BOEYNAEMS, J.
Advances in signalling by extracellular nucleotides: the role and
transduction mechanisms of P2Y receptors.
CELL SIGNAL. 12 351-360 (2000).
8. ZHANG, F., LUO, L., GUSTAFSON, E., LACHOWICZ, J., SMITH, M., QIAO, X.,
LIU, Y., CHEN, G., PRAMANIK, B., LAZ, T., PALMER, K., BAYNE, M. AND
MONSMA, F.
ADP is the cognate ligand for the orphan G protein-coupled receptor SP1999.
J.BIOL.CHEM. 2001 276 8608-8615 (2001).
9. HOLLOPETER, G., JANTZEN, H.M., VINCENT D., LI, G., ENGLAND, L.,
RAMAKRISHNAN, V., YANG, R.B., NURDEN, P., NURDEN, A., JULIUS, D. AND
CONLEY, P.B.
Identification of the platelet ADP receptor targeted by antithrombotic drugs.
NATURE 409 202-207 (2001).
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| Documentation | G protein-coupled receptors (GPCRs) constitute a vast protein family that
encompasses a wide range of functions (including various autocrine, para-
crine and endocrine processes). They show considerable diversity at the
sequence level, on the basis of which they can be separated into distinct
groups. We use the term clan to describe the GPCRs, as they embrace a group
of families for which there are indications of evolutionary relationship,
but between which there is no statistically significant similarity in
sequence [1,2]. The currently known clan members include the rhodopsin-like
GPCRs, the secretin-like GPCRs, the cAMP receptors, the fungal mating
pheromone receptors, and the metabotropic glutamate receptor family.
The rhodopsin-like GPCRs themselves represent a widespread protein family
that includes hormone, neurotransmitter and light receptors, all of
which transduce extracellular signals through interaction with guanine
nucleotide-binding (G) proteins. Although their activating ligands vary
widely in structure and character, the amino acid sequences of the
receptors are very similar and are believed to adopt a common structural
framework comprising 7 transmembrane (TM) helices [3-5].
In addition to their roles in energy metabolism, extracellular nucleotides
(such as ATP) can act as signalling molecules to induce a wide variety of
biological effects. They are released into the extracellular fluid as a
result of cell lysis, exocytosis of nucleotide-containing granules or by
efflux through membrane transport proteins, and can function as autocrine
and paracrine mediators [6,7]. Nucleotides play a role in synaptic
transmission and in platelet-vessel wall interactions. In neurons of the
central and peripheral nervous system, ATP is colocalised and cosecreted
with more traditional neurotransmitters, such as catecholamines and
acetylcholine, and has excitatory effects [6,7]. ATP is also found in high
concentrations in the dense granules of platelets, together with ADP. These
granules also contain lower levels of other nucleotides, such as adenine
dinucleotides, GTP and UTP [7]. In addition, ADP is released from the
vascular endothelium following injury and causes activation of platelets [6].
Receptors for adenine nucleotides are collectively termed P2 purinoceptors.
They can be further subdivided into two structural classes: P2X receptors
are ligand-gated ion channels, while P2Y receptors are G protein-coupled
receptors. P2Y receptors have also been identified that are selective for
uridine (rather than adenine) nucleotides [7].
cDNA encoding a platelet ADP receptor, designated P2Y12, has been isolated
and functionally characterised [8,9]. The receptor is coupled to the
inhibition of adenylyl cyclase through Gi. In conjunction with P2Y1, P2Y12
receptors mediate ADP-induced platelet aggregation [8,9]. The receptor is a
target of the thienopyridine antithrombotic drugs clopidogrel and
ticlopidine, which have been demonstrated to be effective in treating a
variety of thrombotic diseases [9].
P2Y12PRNCPTR is a 3-element fingerprint that provides a signature for the
P2Y12 purinoceptor. The fingerprint was derived from an initial alignment
of 2 sequences: the motifs were drawn from conserved regions spanning the
C-terminal two thirds of the alignment, focusing on those sections that
characterise the P2Y12 receptors but distinguish them from the rest of the
P2Y receptor family - motif 1 spans part of the second intracellular loop
and part of TM domain 4; motif 2 spans part of the third intracellular loop,
leading into TM domain 6; and motif 3 resides within the cytoplasmic
C-terminal region. Two iterations on SPTR39.22_17.3f were required to reach
convergence, at which point a true set comprising 4 sequences was identified.
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