Characterization of a novel iodocyanopindolol and SM-11044 binding protein, which may mediate relaxation of depolarized rat colon tonus.
Studies under blockade of alpha-, beta1-, and beta2-adrenoreceptors revealed a good correlation between the responses of rat colon relaxation of depolarized tonus and of rat adipocyte lipolysis elicited by catecholamines or BRL-37344, a selective beta3-adrenoreceptor agonist, suggesting beta3-adrenoreceptor stimulation. In contrast, SM-11044, a nonselective beta-adrenoreceptor agonist, stimulated colon relaxation more efficiently than lipolysis; its effects were differently antagonized by cyanopindolol with pA2 values of 8.31 in colon and of 7.32 in adipocytes. Binding studies in rat colon smooth muscle membranes using [125I]iodocyanopindolol under blockade of adrenaline and serotonin receptors revealed the existence of a single class of sites (Kd = 11.0 nM, Bmax = 716.7 fmol/mg protein). The specific binding was saturable and reversible and was displaced by SM-11044 but not by BRL-37344, isoproterenol, noradrenaline, adrenaline, serotonin, nor dopamine. This binding site was photoaffinity labeled using [125I]iodocyanopindolol-diazirine. The labeling was prevented by SM-11044 but not by BRL-37344. The amino-terminal amino acid sequences of the high performance liquid chromatography-purified peptides generated by enzymatic and chemical cleavages of the affinity labeled 34-kDa protein confirmed that the novel iodocyanopindolol or SM-11044 binding protein of rat colon smooth muscle membranes is different from known adrenaline, serotonin, or dopamine receptors. Its functional role might include the relaxation of depolarized colon.
Sugasawa
T
T
Institut Cochin de Génétique Moléculaire, CNRS-UPR 0415 and Université Paris VII, 22 rue Méchain, 75014 Paris, France.
Matsuzaki-Fujita
M
M
Guillaume
J L
JL
Camoin
L
L
Morooka
S
S
Strosberg
A D
AD
D017667:Adipocytes / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000378:metabolism*; D000345:Affinity Labels; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry*; D002396:Catechols / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002474:Cell-Free System; D003106:Colon / Q000378:metabolism*; D020120:Iodocyanopindolol; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009129:Muscle Tonus / Q000187:drug effects*; D009130:Muscle, Smooth / Q000378:metabolism; D010449:Peptide Mapping; D010646:Phentolamine / Q000378:metabolism; D010869:Pindolol / Q000031:analogs & derivatives* / Q000378:metabolism; D011433:Propranolol / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D012694:Serine / Q000031:analogs & derivatives* / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism; D012995:Solubility
D000318:Adrenergic beta-Agonists; D000345:Affinity Labels; D002352:Carrier Proteins; D002396:Catechols; C076952:SM 11044; D012701:Serotonin; D012694:Serine; D020120:Iodocyanopindolol; D011433:Propranolol; D010869:Pindolol; D010646:Phentolamine