Human Complete Androgen Insensitivity with Normal Dihydrotestosterone Receptor Binding Capacity in Cultured Genital Skin Fibroblasts: Evidence for a Qualitative Abnormality of the Receptor*

Abstract

Complete androgen insensitivity syndrome (CAIS), or so-called testicular feminization, results from the lack of androgen action on target organs. Within this syndrome, two major variants have been described. In the first variant, the specific intracellular androgen receptors are undetectable (CAIS, AR-), whereas normal levels of androgen receptors are measured in the second variant (CAIS, AR+). From studies with cultured labial skin fibroblasts of three CAIS, AR+ patients from the same family, we have demonstrated that their androgen receptors present qualitative differences when compared to normal receptors: 1) the apparent affinity constant (Kd) of 5 alpha-dihydrotestosterone for the receptor is higher than normal; 2) the in vitro dissociation rate of the receptor-steroid complex is faster than normal: 3) the cellular androgen receptor is more thermolabile than normal when cells are exposed to superphysiological temperatures; and 4) the relative binding affinity of the androgen receptor for progesterone is greater than normal. These findings suggest the presence of a structural abnormality of the androgen receptor in patients with CAIS, AR+. However, these changes (e.g. slightly decreased affinity of the receptor for 5 alpha-dihydrotestosterone) probably do not explain the total lack of androgen action in these patients. Finally, the present data from this family along with those from the literature suggest the presence of heterogeneity as to the cause of the defect in CAIS, AR+.

Incomplete Androgen Insensitivity Associated with a Thermolabile Androgen Receptor.

“…The presence of thermolabile androgen receptor (qualitatively abnormal androgen receptor) made the diagnosis convincing. Thermolabile androgen receptors have been observed in complete AIS [4,5], incomplete AIS [6], the Reifeinstein syndrome [7] and the infertile male syndrome [8], indicating that patients with thermolabile androgen receptors span a wide spectrum. Further study is required to elucidate these forms of phenotypic heterogeniety in patients with thermolabile androgen receptors.…”

Impaired stimulation of 25-hydroxyvitamin D-24-hydroxylase in fibroblasts from a patient with vitamin D-dependent rickets, type II. A form of receptor-positive resistance to 1,25-dihydroxyvitamin D3.

“…However, when more sensitive techniques were developed to assess qualitative abnormalities of the androgen receptor, only a small fraction of the families with androgen resistance had no identifiable receptor abnormality (27). And, in fact, the first family reported to have receptor-positive androgen resistance (26) has recently been shown to have a qualitatively abnormal androgen receptor (28). Thus, defects in steroid hormone action at a postreceptor site are uncommon.…”

Androgen Receptor Mutations Associated with Androgen Insensitivity Syndrome: A High Content Analysis Approach Leading to Personalized Medicine

“…Cells were initially washed in PBS buffer and fixed for 30 min on ice in 4% formaldehyde prepared in CSK buffer. After fixation, auto-fluorescence was quenched using a 0.1 M NH 4 Cl solution for 10 minutes. Next, cells were permeabilized (30 min) with 0.5% Triton-X.…”

“…mcgill.ca/), and a large body of previous work has defined three broad varieties of AR 3 H-DHT binding abnormalities in monolayer binding analyses: 1) absent binding (i.e. 3 H-DHT binding is undetectable) [3]; 2) qualitatively abnormal binding [e.g., binding is normal but with qualitative abnormalities such as increased ligand dissociation rate (the dissociation rate is considered abnormal if ,60% of the specific androgen binding remains after 3 hours) [4]; or thermolability (defined as a reduction in specific androgen binding at 41uC compared to 37uC of greater than 40%) [5]]; or, 3) decreased binding (e.g., binding is detectable but below normal) [1]. The degree of abnormality caused by each individual mutation is usually related to the patient phenotype, the 3 H-DHT binding characteristics, and the amount of residual reporter gene activity present in cells transfected with an AR carrying that particular mutation; in general, in the more feminized phenotypes, lack of 3 H-DHT binding and abnormal transcriptional activity parallel increasing AR malfunction.…”