Pretreatment of human platelet membranes with trypsin abolishes GTP but not Na+ effects on α2-adrenoreceptor–agonist interactions
| Autor: | Pitambar Somani, Sankaridrug M. Periyasamy |
|---|---|
| Rok vydání: | 1987 |
| Předmět: |
Blood Platelets
Agonist Conformational change Epinephrine GTP' Physiology medicine.drug_class Proteolysis In Vitro Techniques Radioligand Assay Physiology (medical) medicine Humans Magnesium Trypsin Receptor Pharmacology medicine.diagnostic_test Chemistry Sodium Yohimbine General Medicine Receptors Adrenergic alpha Ligand (biochemistry) Kinetics Membrane Biochemistry Guanosine Triphosphate Adrenergic alpha-Agonists medicine.drug |
| Zdroj: | Canadian Journal of Physiology and Pharmacology. 65:778-784 |
| ISSN: | 1205-7541 0008-4212 |
| DOI: | 10.1139/y87-125 |
| Popis: | The affinity of many types of membrane-bound receptors coupled negatively to adenylate cyclase is regulated by divalent and monovalent cations and by guanine nucleotides (GTP). We used α2-adrenoreceptors of human platelets as a model system to find out the effect of limited proteolysis with trypsin on the regulation of the α2-adrenoreceptor–agonist interactions by GTP and Na+. We found that partial proteolysis of the membranes with trypsin for 3 min at 35 °C reduced specific [3H]yohimbine binding to platelet membranes to 40–50% of control. The following characteristics of the receptors remaining after proteolysis were similar to those of untreated membranes: affinity for the agonist and antagonists, stereospecificity, and kinetic properties. Trypsin also did not modify the ability of the receptor's change from a high to low affinity state in the presence of Na+. These findings suggested that the capability of the receptors to recognize the ligand and their ability to undergo a conformational change in the presence of the agonist were retained despite a reduction in the total number of receptors by trypsin. However, the modulation of the receptor–agonist interactions by GTP or Mg2+ was lost in the trypsin-pretreated membranes, while the modulation by Na+ remained intact. It is suggested that the loss of GTP or Mg2+ effects on receptor–ligand interactions produced by trypsin may be due to trypsin-induced disruption of subunits (αi, βγ) interactions of Gi protein. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|