Ser352 and Ser354 in the carboxyl terminus of the human P2Y(1) receptor are required for agonist-promoted phosphorylation and internalization in MDCK cells.
OBJECTIVE
The P2Y(1) receptor promotes chloride secretion in epithelial cells, a process critical for regulation of extracellular ion and fluid levels. Here we have examined the role of phosphorylation in agonist-induced internalization of P2Y(1) receptors.


METHODS
A high-affinity radiolabelled antagonist, MRS2500, was used to quantify cell surface-binding sites of P2Y(1) receptors in Madin-Darby canine kidney (MDCK) epithelial cells, following exposure to agonists. The regions in the carboxyl terminus involved in both agonist-induced internalization of the receptor and its phosphorylation were identified by mutational analysis.


RESULTS
Endogenous and stably expressed recombinant P2Y(1) receptors rapidly internalized with similar time courses in response to agonist in MDCK cells, ensuring that the levels of recombinant receptor achieved by retroviral infection did not adversely affect function of the internalization machinery. Four protein kinase C inhibitors of varying specificity did not affect internalization of recombinant receptors. Agonist-promoted internalization of a series of truncated P2Y(1) receptors identified a region between residues 349 and 359 in the carboxyl terminus as critical for regulation. Two amino acids within this region, Ser352 and Ser354, were shown to be both necessary and sufficient for agonist-promoted receptor phosphorylation and internalization.


CONCLUSIONS
Our results firmly establish Ser352 and Ser354 in the carboxyl terminus of P2Y(1) receptors as critical residues for agonist-induced receptor internalization in MDCK cells. As the mechanism mediating this regulation requires phosphorylation of these key residues, the relevant receptor-regulated protein kinase can now be identified.
Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7365, USA.
Ai-Dong
AD
Qi
Dayle
D
Houston-Cohen
Isabella
I
Naruszewicz
T Kendall
TK
Harden
Robert A
RA
Nicholas
D000818:Animals; D002103:Cadaverine / Q000031:analogs & derivatives / Q000494:pharmacology; D002460:Cell Line; D002966:Clathrin / Q000378:metabolism; D003838:Deoxyadenine Nucleotides / Q000378:metabolism / Q000494:pharmacology; D004285:Dogs; D034281:Dynamins / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects; D005822:Genetic Vectors; D006801:Humans; D006835:Hydrazones / Q000494:pharmacology; D007668:Kidney; D018613:Microscopy, Confocal; D010766:Phosphorylation; D011485:Protein Binding; D058912:Purinergic P2Y Receptor Agonists / Q000494:pharmacology*; D011869:Radioligand Assay; D058472:Receptors, Purinergic P2Y1 / Q000737:chemistry / Q000378:metabolism*; D012694:Serine / Q000378:metabolism
C495475:2-iodo-N(6)-methyl-(N)-methanocarba-2'-deoxyadenosine-3',5'-bisphosphate; D002966:Clathrin; D003838:Deoxyadenine Nucleotides; D006835:Hydrazones; C511794:N'-(3,4-dihydroxybenzylidene)-3-hydroxy-2-naphthahydrazide; D058912:Purinergic P2Y Receptor Agonists; D058472:Receptors, Purinergic P2Y1; D012694:Serine; D034281:Dynamins; C008542:monodansylcadaverine; D002103:Cadaverine