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Chromosomal assignment of the gene for the human beta 2-adrenergic receptor
Abstract:
Chinese hamster fibroblasts (CHW) fail to physiologically respond to the beta-adrenergic agonist isoproterenol with an increase in cellular cAMP. This unresponsiveness is due to a lack of beta-adrenergic receptors as indicated by an absence of specific binding of 125I-labeled hydroxybenzylpindolol (125I-HYP) to CHW plasma membranes. Preparation of somatic cell hybrids between CHW and human peripheral blood leukocytes led to the selection of a panel of 15 human-Chinese hamster cell hybrid clones, some of which had beta 2-adrenergic receptors (specifically bound 125I-HYP) and responded to isoproterenol (accumulated cAMP). Biochemical analysis of independent cloned cell hybrids indicated that beta 2-adrenergic receptor density and the intensity of the associated physiological response were closely correlated (r = 0.98). Both of these parameters were concordant in all cell hybrids with the presence of human chromosome 5. All other human chromosomes could be ruled out. These results suggest that the structural gene for the beta 2-adrenergic receptor is found on human chromosome 5.
Insights
Chinese hamster cells lack beta-adrenergic receptors, preventing a key cellular response. Hybrid cells revealed that human chromosome 5 carries the gene for these essential beta-adrenergic receptors.
Area of Science:
- Cell Biology
- Genetics
- Pharmacology
Background:
- Chinese hamster fibroblasts (CHW) do not exhibit a cAMP increase when treated with the beta-adrenergic agonist isoproterenol.
- This unresponsiveness is attributed to a deficiency of beta-adrenergic receptors, evidenced by the lack of specific binding of 125I-labeled hydroxybenzylpindolol (125I-HYP) to CHW plasma membranes.
Purpose of the Study:
- To identify the genetic basis for beta-adrenergic receptor expression and function in Chinese hamster fibroblasts.
- To determine which human chromosome, if any, is responsible for restoring beta-adrenergic responsiveness in CHW cells.
Main Methods:
- Somatic cell hybridization was employed, creating hybrid clones from CHW cells and human peripheral blood leukocytes.
- A panel of 15 human-Chinese hamster cell hybrid clones was selected and analyzed for the presence of beta-adrenergic receptors and their physiological response.
- Binding assays using 125I-HYP and cAMP accumulation measurements were performed on the hybrid clones.
Main Results:
- Several hybrid clones acquired beta-adrenergic receptors and demonstrated a physiological response to isoproterenol, including increased cAMP levels.
- A strong correlation (r = 0.98) was observed between beta-adrenergic receptor density and the intensity of the cellular response.
- The presence of these parameters in the hybrid clones consistently matched the presence of human chromosome 5, while other human chromosomes were excluded.
Conclusions:
- The structural gene encoding the beta-adrenergic receptor is localized to human chromosome 5.
- This finding provides critical insight into the genetic control of beta-adrenergic receptor function and cellular signaling pathways.