Truncation of the carboxyl-terminal region of the rat parathyroid hormone (PTH)/PTH-related peptide receptor enhances PTH stimulation of adenylyl cyclase but not phospholipase C.
The functional role of the rat parathyroid hormone(PTH)/PTH-related peptide (PTHrP) receptor's carboxyl-terminal region was characterized by comparing the binding and signaling properties of receptors that have 78 and 111 amino acid deletions (R513 and R480, respectively), with those of the 591-amino acid wild-type (WT) receptor. R480 and R513 have 4- and 1.5-fold lower apparent Kd values for rat PTH-(1-34) (rPTH), compared with the WT receptor (WT, 1.81 +/- 0.19 nM; R513, 1.24 +/- 0.12 nM; R480, 0.48 +/- 0.05 nM, mean +/- S.E.). PTH (100 nM)-stimulated cAMP accumulation and polyphosphoinositide hydrolysis both correlated positively with receptor expression. However, whereas PTH-stimulated polyphosphoinositide hydrolysis was indistinguishable among WT and either truncated mutant at comparable levels of expressed receptors, maximal PTH-stimulated cAMP accumulation was 4-6- and 2-3-fold higher in cells expressing R480 and R513, respectively. Furthermore, pretreatment of COS-7 cells with 100 ng/ml of pertussis toxin (PTX) enhanced PTH-stimulated cAMP accumulation in cells expressing the WT receptor, but failed to do so in cells expressing either R480 or R513. Thus, sequences in the PTH/PTHrP receptor's carboxyl-terminal tail lower the affinity of the WT receptor for agonist; directly interact with, or indirectly facilitate the interaction of the receptor with a PTX-sensitive G protein that inhibits adenylyl cyclase; and decrease the efficacy with which the receptor interacts with Gs.
Iida-Klein
A
A
Endocrine Unit, Massachusetts General Hospital, Boston 02114, USA.
Guo
J
J
Xie
L Y
LY
Jüppner
H
H
Potts
J T
JT
Kronenberg
H M
HM
Bringhurst
F R
FR
Abou-Samra
A B
AB
Segre
G V
GV
D037361:Adenylate Cyclase Toxin; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D010281:Parathyroid Hormone / Q000378:metabolism*; D037342:Pertussis Toxin; D011869:Radioligand Assay; D051381:Rats; D044168:Receptor, Parathyroid Hormone, Type 1; D018016:Receptors, Parathyroid Hormone / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D010281:Parathyroid Hormone; D044168:Receptor, Parathyroid Hormone, Type 1; D018016:Receptors, Parathyroid Hormone; D010566:Virulence Factors, Bordetella; D000242:Cyclic AMP; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases