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Effects of the ?-agonist, isoprenaline, on the down-regulation, functional responsiveness and trafficking of ?2-adrenergic receptors with N-terminal polymorphisms.

ABSTRACT: The ?2-AR (?2-adrenergic receptor) is an important target for respiratory and CVD (cardiovascular disease) medications. Clinical studies suggest that N-terminal polymorphisms of ?2-AR may act as disease modifiers. We hypothesized that polymorphisms at amino acids 16 and 27 result in differential trafficking and down-regulation of ?2-AR variants following ?-agonist exposure. The functional consequences of the four possible combinations of these polymorphisms in the human ?2-AR (designated ?2-AR-RE, ?2-AR-GE, ?2-AR-RQ and ?2-AR-GQ) were studied using site-directed mutagenesis and recombinant expression in HEK-293 cells (human embryonic kidney cells). Ligand-binding assays demonstrated that after 24 h exposure to 1 ?M isoprenaline, isoforms with Arg16 (?2-AR-RE and ?2-AR-RQ) underwent increased down-regulation compared with isoforms with Gly16 (?2-AR-GE and ?2-AR-GQ). Consistent with these differences in down-regulation between isoforms, prolonged isoprenaline treatment resulted in diminished cAMP response to subsequent isoprenaline challenge in ?2-AR-RE relative to ?2-AR-GE. Confocal microscopy revealed that the receptor isoforms had similar co-localization with the early endosomal marker EEA1 following isoprenaline treatment, suggesting that they had similar patterns of internalization. None of the isoforms exhibited significant co-localization with the recycling endosome marker Rab11 in response to isoprenaline treatment. Furthermore, we found that prolonged isoprenaline treatment led to a higher degree of co-localization of ?2-AR-RE with the lysosomal marker LAMP1 (lysosome-associated membrane protein 1) compared with that of ?2-AR-GE. Taken together, these results indicate that a mechanism responsible for differential responses of these receptor isoforms to the ?-agonist involves differences in the efficiency with which agonist-activated receptors are trafficked to the lysosomes for degradation, or differences in degradation in the lysosomes.

SUBMITTER: Koryakina Y

PROVIDER: S-EPMC4018189 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Effects of the β-agonist, isoprenaline, on the down-regulation, functional responsiveness and trafficking of β2-adrenergic receptors with N-terminal polymorphisms.

Koryakina Yulia Y Jones Stacie M SM Cornett Lawrence E LE Seely Kathryn K Brents Lisa L Prather Paul L PL Kofman Alexander A Kurten Richard C RC

Cell biology international 20120101 12

The β2-AR (β2-adrenergic receptor) is an important target for respiratory and CVD (cardiovascular disease) medications. Clinical studies suggest that N-terminal polymorphisms of β2-AR may act as disease modifiers. We hypothesized that polymorphisms at amino acids 16 and 27 result in differential trafficking and down-regulation of β2-AR variants following β-agonist exposure. The functional consequences of the four possible combinations of these polymorphisms in the human β2-AR (designated β2-AR-R ...[more]

PMID: 22938397

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Project description:Evidence suggests that variation in the length of the poly-C repeat in the 3' untranslated region (3'UTR) of the ?2-adrenergic receptor gene (ADRB2) may contribute to interindividual variation in ?-agonist response. However, methodology in previous studies limited the assessment of the effect of sequence variation in the context of poly-C repeat length. The objectives of this study were to design a novel genotyping method to fully characterize sequence variation in the ADRB2 3'UTR poly-C repeat in asthma patients treated with inhaled corticosteroid and long-acting ?2-adrenergic agonist (ICS/LABA) combination therapy, and to analyze the effect of the poly-C repeat polymorphism on clinical response.In 2,250 asthma patients randomized to treatment with budesonide/formoterol or fluticasone/salmeterol in a six-month study (AstraZeneca study code: SD-039-0735), sequence diversity in the ADRB2 poly-C repeat region was determined using a novel sequencing-based genotyping method. The relationship between the poly-C repeat polymorphism and the incidence of severe asthma exacerbations, and changes in pulmonary function and asthma symptoms from baseline to the average during the treatment period, were analyzed.Poly-C repeat genotypes were assigned in 97% (2,192/2,250) of patients. Of the 13 different poly-C repeat alleles identified, six alleles occurred at a frequency of >5% in one or more population in this study. The repeat length of these six common alleles ranged from 10 to 14 nucleotides. Twelve poly-C repeat genotypes were observed at a frequency of >1%. No evidence of an association between poly-C repeat genotype and the incidence of severe asthma exacerbations was observed. Patients' pulmonary function measurements improved and asthma symptoms declined when treated with ICS/LABA combination therapy regardless of poly-C repeat genotype.The extensive sequence diversity present in the poly-C repeat region of the ADRB2 3'UTR did not predict therapeutic response to ICS/LABA therapy.

Dataset Information

Effects of the ?-agonist, isoprenaline, on the down-regulation, functional responsiveness and trafficking of ?2-adrenergic receptors with N-terminal polymorphisms.

Publications

Effects of the β-agonist, isoprenaline, on the down-regulation, functional responsiveness and trafficking of β2-adrenergic receptors with N-terminal polymorphisms.

Similar Datasets

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