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Structural and functional alterations in the β2‐adrenoceptor are caused by a point mutation in patients with atopic eczema
Author(s) -
Schallreuter Karin U.,
Wei Yuwang,
Pittelkow Mark R.,
Swanson Norma N.,
Gibbons Nicholas C. J.,
Wood John M.
Publication year - 2007
Publication title -
experimental dermatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.108
H-Index - 96
eISSN - 1600-0625
pISSN - 0906-6705
DOI - 10.1111/j.1600-0625.2007.00600.x
Subject(s) - point mutation , receptor , endocrinology , mutation , heterozygote advantage , atopy , microbiology and biotechnology , medicine , immunology , immunoglobulin e , gene , biology , chemistry , allele , genetics , antibody , allergy
The density of β2‐adrenoceptors is significantly decreased in both keratinocytes and peripheral blood lymphocytes from patients with atopic eczema. Furthermore both cell types showed a sixfold increase in the K D for the specific binding of the non‐specific antagonists (–)‐[ 3 H]CGP 12177 and [ 125 I]CYP to keratinocytes and lymphocytes respectively compared with healthy controls. Based on these results polymorphism in the β2‐adrenoceptor gene was suspected. Consequently the entire intronless β2‐adrenoceptor gene was isolated from whole blood and by RT‐PCR from keratinocyte extracts of nine patients with atopic eczema and four healthy controls. DNA sequence analysis of nine atopic eczema patients confirmed a substitution in codon (1618) GCC (Ala 119 ) to GAC (Asp 119 ). This point mutation is expressed on the third transmembrane helix only 13Å away from the established agonist/antagonist binding site at Asp 113 . Computer modelling of this third transmembrane helix revealed substantial structural changes in the mutant compared with the wild type. Epidermal keratinocytes were established from one patient with atopic eczema (homozygote), the mother (heterozygote) and one age‐matched healthy control. Cells were grown in media containing different concentrations of l ‐phenylalanine and receptor densities were determined. The results showed that cells with atopic eczema showed an increased sensitivity to l ‐phenylalanine concentrations with a narrow homeostasis compared with healthy controls. The heterozygous mother was only 50% as sensitive as the child. In summary, the results indicate that atopic eczema is associated with a single point mutation in the β2‐adrenoceptor gene leading to an impaired adrenergic response in the epidermis of these patients.