Discovery of a functional immunoreceptor tyrosine-based switch motif in a 7-transmembrane-spanning receptor: role in the orexin receptor OX1R-driven apoptosis.
The orexin neuropeptides promote robust apoptosis in cancer cells. We have recently shown that the 7-transmembrane-spanning orexin receptor OX1R mediates apoptosis through an original mechanism. OX1R is equipped with a tyrosine-based inhibitory motif ITIM, which is tyrosine-phosphorylated on receptor activation, allowing the recruitment and activation of the tyrosine phosphatase SHP-2, leading to apoptosis. We show here that another motif, immunoreceptor tyrosine-based switch motif (ITSM), is present in OX1R and is mandatory for OX1R-mediated apoptosis. This conclusion is based on the following observations: 1) a canonical ITSM sequence is present in the first intracellular loop of OX1R; 2) mutation of Y(83) to F within ITSM abolished OX1R-mediated apoptosis but did not alter orexin-induced inositol phosphate formation or calcium transient via coupling of OX1R to G(q) protein; 3) mutation of Y(83) to F further abolished orexin-induced tyrosine phosphorylation in ITSM and subsequent recruitment of SHP-2 by the receptor. Finally, we developed a structural model of OX1R showing that the spatial localization of phosphotyrosines in ITSM and ITIM in OX1R is compatible with their interaction with the two SH2 domains of SHP-2. These data represent the first evidence for a functional role of an ITSM in a 7-transmembrane-spanning receptor.
El Firar
Aadil
A
INSERM U773, Centre de Recherche Biomédicale Bichat Beaujon CRB3, F-75018, Paris.
Voisin
Thierry
T
Rouyer-Fessard
Christiane
C
Ostuni
Mariano A
MA
Couvineau
Alain
A
Laburthe
Marc
M
D020816:Amino Acid Motifs; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D016466:CHO Cells; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008958:Models, Molecular; D009479:Neuropeptides / Q000378:metabolism; D064446:Orexin Receptors; D000068797:Orexins; D011487:Protein Conformation; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018013:Receptors, Neuropeptide / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins
D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D064446:Orexin Receptors; D000068797:Orexins; D043562:Receptors, G-Protein-Coupled; D018013:Receptors, Neuropeptide; D011994:Recombinant Proteins