Mutation of the phosphorylatable residue Thr429 in Glu of the human VPAC1 led to a constitutively desensitized receptor.
The hVPAC1 receptor is rapidly phosphorylated and internalized by agonists but not re-expressed at the membrane after washing. Mutation of Ser/Thr residues in the C-terminus reduced phosphorylation but not internalization that was abolished only when all the phosphorylatable residues were mutated. Substitution of Thr429 by Glu mimicking a phosphothreonin led to a mutant with unchanged binding properties, decreased coupling to adenylate cyclase consisting in a reduced VIP potency, increased basal and VIP stimulated phosphorylation, preserved internalization followed by a rapid receptor re-expression. These are the expected characteristics of a constitutively desensitized receptor, putting forward the role of Thr429 phosphorylation in that process.
Laboratoire de Chimie Biologique et de la Nutrition, School of Medicine, Université Libre de Bruxelles, 808 Route de Lennik-CP611, B-1070 Bruxelles, Belgium.
Christelle
C
Langlet
Ingrid
I
Nachtergael
Patrick
P
Robberecht
Ingrid
I
Langer
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D018698:Glutamic Acid / Q000737:chemistry*; D006801:Humans; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I / Q000737:chemistry*; D013912:Threonine / Q000737:chemistry*
D010455:Peptides; D051238:Receptors, Vasoactive Intestinal Polypeptide, Type I; D013912:Threonine; D018698:Glutamic Acid; D000262:Adenylyl Cyclases