Structural basis of K63-ubiquitin chain formation by the Gordon-Holmes syndrome RBR E3 ubiquitin ligase RNF216.

An increasing number of genetic diseases are linked to deregulation of E3 ubiquitin ligases. Loss-of-function mutations in the RING-between-RING (RBR) family E3 ligase RNF216 (TRIAD3) cause Gordon-Holmes syndrome (GHS) and related neurodegenerative diseases. Functionally, RNF216 assembles K63-linked ubiquitin chains and has been implicated in regulation of innate immunity signaling pathways and synaptic plasticity. Here, we report crystal structures of key RNF216 reaction states including RNF216 in complex with ubiquitin and its reaction product, K63 di-ubiquitin. Our data provide a molecular explanation for chain-type specificity and reveal the molecular basis for disruption of RNF216 function by pathogenic GHS mutations. Furthermore, we demonstrate how RNF216 activity and chain-type specificity are regulated by phosphorylation and that RNF216 is allosterically activated by K63-linked di-ubiquitin. These molecular insights expand our understanding of RNF216 function and its role in disease and further define the mechanistic diversity of the RBR E3 ligase family.

Androgen-dependent miR-125a-5p targets LYPLA1 and regulates global protein palmitoylation level in late-onset hypogonadism males.

Late-onset hypogonadism (LOH) is defined as a clinical and biochemical syndrome with multiple symptoms caused by testosterone deficiency in aging males. An in-depth exploration of the molecular mechanism underlying LOH development is insufficient. We previously identified miR-125a-5p as a dysregulated microRNA in LOH patients and potential diagnostic biomarker for LOH. The present study demonstrated that plasma miR-125a-5p was upregulated after testosterone supplementation in both LOH patients and castrated mice, and positively associated with the testosterone concentrations, suggesting direct regulation of miR-125a-5p expression by testosterone. Androgen response element in the promoter of miR-125a-5p was subsequently identified. Target gene screening and confirmation verified that LYPLA1, encoding acyl-protein thioesterase 1 which catalyzed protein depalmitoylation process, was a target gene of miR-125a-5p. Furthermore, in cells cultured with testosterone deprivation and organs from castrated mice, testosterone deficiency led to decreased global protein palmitoylation level. In aging males, global protein palmitoylation in peripheral blood showed a notable decline in LOH patients contrast to the normal elderly males. And the palmitoylation level was positively correlative with serum testosterone concentrations. Our results suggested that testosterone could regulate global palmitoylation level through miR-125a-5p/LYPLA1 signaling pathway. Given that protein palmitoylation is pivotal for protein function and constitutes the pathogenesis of various diseases, testosterone/miR-125a-5p/LYPLA1 may contribute to the molecular mechanism underlying multiple symptoms caused by testosterone deficiency in LOH patients, and aberrant global palmitoylation could be a potential biomarker for LOH.

Testosterone Increases the Expression and Phosphorylation of AMP Kinase α in Men With Hypogonadism and Type 2 Diabetes.

CONTEXT: Adenosine 5'-monophosphate-activated protein kinase-α (AMPKα) is a mediator of exercise-induced glucose uptake in skeletal muscle. OBJECTIVE: We evaluated whether AMPKα expression and phosphorylation are reduced in skeletal muscle and adipose tissue of patients with hypogonadotropic hypogonadism (HH), and whether testosterone replacement therapy results in restoration of the expression and phosphorylation of AMPKα. DESIGN: This is a secondary analysis of a previously completed trial that showed an insulin-sensitizing effect of testosterone therapy in men with type 2 diabetes and HH. SETTING: Clinical research center at university. PATIENTS: Thirty-two men with HH and 32 eugonadal men were compared at baseline. INTERVENTIONS: Men with HH were treated with intramuscular injections of testosterone or placebo every 2 weeks for 22 weeks. Quadriceps muscle biopsies and subcutaneous abdominal fat biopsies were obtained before and after 4-hour euglycemic hyperinsulinemic clamp, prior to and after testosterone or placebo therapy. OUTCOME MEASURES AND RESULTS: mRNA expression of AMPKα in hypogonadal men was lower by 37% in adipose tissue and 29% in skeletal muscle, respectively, compared with levels in eugonadal men, while phosphorylated AMPKα was lower by 22% and 28%, respectively. Following testosterone replacement, the expression of AMPKα did not alter in the fasting state but increased markedly by 41% and 46% in adipose tissue and muscle, respectively, after the clamp. In contrast, phosphorylated AMPKα increased by 69% in muscle after testosterone therapy but did not change following the clamp. CONCLUSIONS: Testosterone modulates the expression of AMPKα and phosphorylated AMPKα. These effects may contribute to the improved insulin sensitivity following testosterone therapy.

Ataxia and hypogonadism caused by the loss of ubiquitin ligase activity of the U box protein CHIP.

Gordon Holmes syndrome (GHS) is a rare Mendelian neurodegenerative disorder characterized by ataxia and hypogonadism. Recently, it was suggested that disordered ubiquitination underlies GHS though the discovery of exome mutations in the E3 ligase RNF216 and deubiquitinase OTUD4. We performed exome sequencing in a family with two of three siblings afflicted with ataxia and hypogonadism and identified a homozygous mutation in STUB1 (NM_005861) c.737C→T, p.Thr246Met, a gene that encodes the protein CHIP (C-terminus of HSC70-interacting protein). CHIP plays a central role in regulating protein quality control, in part through its ability to function as an E3 ligase. Loss of CHIP function has long been associated with protein misfolding and aggregation in several genetic mouse models of neurodegenerative disorders; however, a role for CHIP in human neurological disease has yet to be identified. Introduction of the Thr246Met mutation into CHIP results in a loss of ubiquitin ligase activity measured directly using recombinant proteins as well as in cell culture models. Loss of CHIP function in mice resulted in behavioral and reproductive impairments that mimic human ataxia and hypogonadism. We conclude that GHS can be caused by a loss-of-function mutation in CHIP. Our findings further highlight the role of disordered ubiquitination and protein quality control in the pathogenesis of neurodegenerative disease and demonstrate the utility of combining whole-exome sequencing with molecular analyses and animal models to define causal disease polymorphisms.

Heparan sulfate 6-O-sulfotransferase 1, a gene involved in extracellular sugar modifications, is mutated in patients with idiopathic hypogonadotrophic hypogonadism.

Neuronal development is the result of a multitude of neural migrations, which require extensive cell-cell communication. These processes are modulated by extracellular matrix components, such as heparan sulfate (HS) polysaccharides. HS is molecularly complex as a result of nonrandom modifications of the sugar moieties, including sulfations in specific positions. We report here mutations in HS 6-O-sulfotransferase 1 (HS6ST1) in families with idiopathic hypogonadotropic hypogonadism (IHH). IHH manifests as incomplete or absent puberty and infertility as a result of defects in gonadotropin-releasing hormone neuron development or function. IHH-associated HS6ST1 mutations display reduced activity in vitro and in vivo, suggesting that HS6ST1 and the complex modifications of extracellular sugars are critical for normal development in humans. Genetic experiments in Caenorhabditis elegans reveal that HS cell-specifically regulates neural branching in vivo in concert with other IHH-associated genes, including kal-1, the FGF receptor, and FGF. These findings are consistent with a model in which KAL1 can act as a modulatory coligand with FGF to activate the FGF receptor in an HS-dependent manner.

Testosterone action on erythropoiesis does not require its aromatization to estrogen: Insights from the testosterone and estrogen treatment of two aromatase-deficient men.

Androgens act on erythropoiesis, but the relative role of testosterone (T) and estradiol (E(2)) on erythropoietic parameters in men is a poorly investigated issue. In order to evaluate separately the effects on erythropoiesis of high-dose T administration alone and of physiological dose of E(2) administration alone two adult men with aromatase deficiency were assessed before and during each treatment. Blood cell count, hemoglobin (Hb), hematocrit (Hct), erythrocyte mean cell volume (MCV), erythrocyte mean corpuscular hemoglobin (MCH), erythrocyte mean corpuscular hemoglobin concentration (MCHC), serum ferritin, iron and total iron-binding capacity (TIBC), serum erythropoietin, serum total testosterone and estradiol were evaluated. Hb, Hct and red cell count rose during testosterone treatment, consistently with the increase in circulating testosterone, but failed to increase during estradiol treatment. A decrease in Hb, Hct and red cell count was recorded in one of the two subjects during estradiol treatment, with a concomitant decrease in serum testosterone. Circulating T alone is capable of and sufficient to influence erythropoiesis, especially at supraphysiological dosage, while circulating E(2) have not the same effect on erythropoietic parameters, suggesting the hypothesis that the erythropoietic changes induced by androgens are not mediated via its aromatization to estrogens.

Partial 17alpha-hydroxylase/17,20-lyase deficiency-clinical report of five Chinese 46,XX cases.

OBJECTIVES: To summarize the clinical characteristics of partial 17alpha-hydroxylase/17,20-lyase deficiency (17OHD) in 46,XX Chinese patients. METHODS: Five cases of 46,XX partial 17OHD from Peking Union Medical College Hospital were studied retrospectively by summarizing and analyzing their clinical data. The molecular pathogenic mechanisms involved are discussed after reviewing the literature. RESULTS: Both complete and partial 17OHD patients have hypergonadotropic hypogonadism and elevated serum levels of adrenocorticotropic hormone and mineralocorticoids. The clinical characteristics of partial 17OHD are different from those of complete 17OHD; patients with the former having various degrees of estrogenic and androgenic impacts such as the development of breasts and pubic hair, and oligomenorrhea or secondary amenorrhea. Elevated serum progesterone with or without elevated serum 17alpha-hydroxyprogesterone and recurrent ovarian cysts are typical manifestations of partial 17OHD. Furthermore, hypokalemic hypertension may be absent in partial 17OHD. The 46,XX partial 17OHD should be differentiated from pure gonadal dysgenesis, premature ovarian failure and polycystic ovarian syndrome. It has been reported that specific mutations of the CYP17 gene can cause partial loss of 17alpha-hydroxylase/17,20-lyase activities or dissociation between the 17alpha-hydroxylase and the 17,20-lyase functions. Oral contraceptive pills are effective for artificial menstruation, but not for the correction of hormone deficiency. A low dose of cortisol should be prescribed in the presence of hypokalemic hypertension. CONCLUSION: The congenital partial 17OHD should be included in the differential diagnosis of menstrual disorders. In these cases, elevated progesterone offers a valuable clue for further investigation.

Substitution mutation C268Y causes 17 beta-hydroxysteroid dehydrogenase 3 deficiency.

The 17 beta-hydroxysteroid dehydrogenase (HSD) type 3 isozyme catalyzes the conversion of androstenedione to testosterone in the testis. Deleterious mutations in the HSD17B3 gene cause undermasculinization in genetic males attributable to impaired testosterone biosynthesis. Hence, a hallmark of this autosomal recessive disorder is a decreased plasma testosterone-to-androstenedione ratio. Here, a novel C268Y substitution mutation in exon 10 of the HSD17B3 gene, in a subject with 17 beta-HSD 3 deficiency, is reported. Reconstitution experiments with recombinant protein reveal that substitution of tyrosine for cysteine at position 268 of 17 beta-HSD type 3 abrogates the enzymatic activity. This finding brings to 20 the number of mutations in the HSD17B3 gene that cause male undermasculinization.

Development of cytochrome P450 aromatase mRNA levels and enzyme activity in ovaries of normal and hypogonadal (hpg) mice.

The cytochrome P450 aromatase (P450arom) enzyme is required for bioconversion of androgen to oestrogen. In this study ovarian P450arom mRNA and enzyme activity have been measured during development in normal mice and hypogondal (hpg) mice which lack circulating gonadotrophins. A semi-quantitative reverse transcription-PCR (RT-PCR) technique was used to measure cytochrome P450arom mRNA levels and aromatase enzyme activity was measured directly. Using RT-PCR, P450arom mRNA was detectable in the adult mouse ovary and also in the uterus, kidney, brain and skeletal muscle but not in cardiac smooth muscle. In the normal mouse, P450arom mRNA was detectable in the ovary on the day of birth (day 1) and levels increased significantly up to day 15 with the most marked changes seen between days 1 and 5. Aromatase activity was also detectable at all ages in the ovary and increased significantly between days 1 and 7. In ovaries from hpg mice, normal levels of P450arom mRNA were present on day 1 but there was no significant change in P450arom mRNA at later ages up to day 15. These results show that in the newborn mouse ovary, which contains only primordial follicles, there is a basal expression of P450arom mRNA which is not gonadotrophin-dependent. After 1 day, however, gonadotrophins are required for normal expression of ovarian P450arom and this coincides with development of primary and secondary follicles.

A syndrome of female pseudohermaphrodism, hypergonadotropic hypogonadism, and multicystic ovaries associated with missense mutations in the gene encoding aromatase (P450arom).

We report the features of a new syndrome of aromatase deficiency due to molecular defects in the CYP19 (P450arom) gene in a 46,XX female. At birth, the patient presented with a nonadrenal form of female pseudohermaphrodism. At 17 months of age, laparotomy revealed normal female internal genital structures; the histological appearance of the ovaries was normal. FSH concentrations were markedly elevated at 9.4 ng/mL LER 869, and estrone and estradiol levels were undetectable (< 37 pmol/L). By 14 yr of age, she had failed to exhibit breast development. The clitoris had enlarged to 4 x 2 cm, and pubic hair was Tanner stage IV. The plasma concentration of testosterone was elevated at 3294 pmol/L, as was androstenedione at 9951 pmol/L. Plasma estradiol levels were below 37 pmol/L. ACTH and dexamethasone tests indicated a nonadrenal source of testosterone and androstenedione. Plasma gonadotropin levels were in the castrate range. Pelvic sonography and magnetic resonance imaging showed multiple 4- to 6-cm ovarian cysts bilaterally. Despite increased circulating androgens and clitoral growth, the bone age was 10 yr at chronologic age 14 2/12 yr. Estrogen replacement therapy resulted in a growth spurt, breast development, menarche, suppression of gonadotropin levels, and resolution of the cysts. The clinical findings suggested the diagnosis of P450arom deficiency. Analyses of genomic DNA from ovarian fibroblasts demonstrated two single base changes in the coding region of the P450arom gene, one at 1303 basepairs (C-T), R435C, and the other at 1310 basepairs (G-A), C437Y, in exon 10. The molecular genetic studies indicate that the patient is a compound heterozygote for these mutations. Expression of these mutations showed that the R435C mutation had 1.1% the activity of the wild-type P450arom enzyme, whereas the C437Y mutation demonstrated no activity. The cardinal features of this syndrome are a consequence of P450arom deficiency: 1) the fetal masculinization in this syndrome can be ascribed to defective placental conversion of C19 steroids to estrogens, leading to exposure of the female fetus to excessive amounts of testosterone; 2) the pubertal failure, mild virilization, multicystic ovaries, and hyperstimulation of the ovaries by FSH and LH are the result of the inability of the ovary to aromatize testosterone and androstenedione to estrogens; and 3) the striking delay in bone age at 14 2/12 yr supports the notion that estrogens, in contrast to androgens, are the major sex steroid driving skeletal maturation during puberty. Familial P450arom deficiency, although rare, may be more common than previously suspected.(ABSTRACT TRUNCATED AT 400 WORDS)

Molecular basis of aromatase deficiency in an adult female with sexual infantilism and polycystic ovaries.

We identified two mutations in the CYP19 gene responsible for aromatase deficiency in an 18-year-old 46,XX female with ambiguous external genitalia at birth, primary amenorrhea and sexual infantilism, and polycystic ovaries. The coding exons, namely exons II-X, of the CYP19 gene were amplified by PCR from genomic DNA and sequenced directly. Direct sequencing of the amplified DNA from the patient revealed two single-base changes, at bp 1303 (C-->T) and bp 1310 (G-->A) in exon X, which were newly found missense mutations and resulted in codon changes of R435C and C437Y, respectively. Subcloning followed by sequencing confirmed that the patient is a compound heterozygote. The results of restriction fragment length polymorphism analysis and direct sequencing of the amplified exon X DNA from the patient's mother indicate maternal inheritance of the R435C mutation. Transient expression experiments showed that the R435C mutant protein had approximately 1.1% of the activity of the wild type, whereas C437Y was totally inactive. Cysteine-437 is the conserved cysteine in the heme-binding region believed to serve as the fifth coordinating ligand of the heme iron. To our knowledge, this patient is the first adult to have described the cardinal features of a syndrome of aromatase deficiency. Recognition that such defects exist will lead to a better understanding of the role of this enzyme in human development and disease.

Male hypogonadism with gynecomastia caused by late-onset deficiency of testicular 17-ketosteroid reductase.

BACKGROUND: 17-Ketosteroid reductase deficiency results in male pseudohermaphroditism because conversion of the weak androgen androstenedione to the more potent androgen testosterone is impaired. If a late-onset form exists, hypogonadism and gynecomastia caused by decreased testosterone production and increased estrogen production, respectively, would be expected as the major clinical manifestations in men. METHODS: We studied 48 male subjects, ranging from 14 to 26 years of age, who had idiopathic pubertal gynecomastia. Serum concentrations of gonadal and adrenal steroid hormones were measured before and after the administration of corticotropin and after the combined administration of chorionic gonadotropin and dexamethasone for three days. RESULTS: We identified three unrelated subjects (ages, 16, 17, and 26 years) with results indicative of a partial deficiency of testicular 17-ketosteroid reductase. The three subjects had gynecomastia as well as decreased libido and impotence. Their mean (+/- SD) base-line serum androstenedione and estrone concentrations were elevated as compared with the levels in the 45 subjects without this enzyme deficiency (androstenedione, 380 +/- 70 vs. 110 +/- 70 ng per deciliter [13 +/- 2 vs. 4 +/- 2 nmol per liter]; estrone, 138 +/- 12 vs. 46 +/- 9 pg per milliliter [511 +/- 44 vs. 170 +/- 33 pmol per liter]). After the administration of chorionic gonadotropin, the mean serum androstenedione concentration in these three subjects was 910 +/- 48 ng per deciliter (32 +/- 2 nmol per liter) and the mean serum estrone concentration was 260 +/- 16 pg per milliliter (962 +/- 59 pmol per liter). The mean serum testosterone concentration at base line was 210 +/- 80 ng per deciliter (7.4 +/- 2.8 nmol per liter) in the 3 subjects, as compared with a value of 410 +/- 12 ng per deciliter (14.4 +/- 0.42 nmol per liter) in the 45 other subjects, and it did not increase in response to the administration of chorionic gonadotropin. The concentrations of androstenedione and estrone in spermatic venous serum were 19 times higher and 73 times higher, respectively, than in normal men. The serum concentrations of follicle-stimulating hormone and luteinizing hormone in these three subjects were inappropriately low, suggesting the presence of hypogonadotropic hypogonadism. CONCLUSIONS: A late-onset form of testicular 17-ketosteroid reductase deficiency can cause gynecomastia and hypogonadism in men.

[Clinical features and diagnosis of mild 3-beta-hydroxysteroid dehydrogenase deficiency in men]. / Klinik und Diagnostik bei Männern mit leichtem 3 beta-Hydroxysteroiddehydrogenase-Mangel.

3 beta-hydroxysteroid dehydrogenase (HSD) deficiency was demonstrated in six males, aged between 18 and 24 years, who had gynaecomastia, hypogonadism or infertility. The predominant laboratory finding was a striking elevation of dehydroepiandrosterone sulphate (DHEAS) levels. The diagnosis of HSD deficiency was confirmed by finding a marked rise in dehydroepiandrosterone (DHEA) and 17-hydroxypregnenolone levels. In contrast to these findings in late-onset enzyme deficiency, in four males with the classical form of 21-hydroxylase deficiency the only sign was a reduction in adult height. The prevalence of late-onset HSD deficiency in men is not known and may be more relevant in patients with gynaecomastia or abnormal gonadal function than has hitherto been realized.

Increase in hepatic lipase activity after testosterone substitution in men with hypogonadism of pituitary origin.

Ten men with hypogonadism of pituitary origin were studied before and during testosterone substitution therapy with regard to effects on the activities of hepatic lipase (HL) and lipoprotein lipase (LPL) in postheparin plasma, and on plasma lipoprotein concentrations. The mean (+/- SEM) testosterone level increased from 1.8 +/- 0.5 to 16.3 +/- 2.4 nmol/l. The mean activity of HL rose from 327.1 +/- 35.2 to 432.8 +/- 57.2 mU/ml (p less than 0.02), while the activity of LPL did not change significantly, 71.0 +/- 9.1 mU/ml before and 62.2 +/- 3.8 mU/ml after treatment. No significant alterations in lipoprotein concentrations were recorded. These results indicate that a normal testosterone level is of importance for maintaining the activity of HL in men, thereby contributing to the sex difference previously recorded for HL activity.

Decrease of aldolase and pyruvate kinase activity in erythrocytes of individuals with male hypogonadism as an expression of lack of androgen influence on the bone marrow.

The authors have demonstrated the statistically significant decrease of aldolase and pyruvate kinase activity in erythrocytes in a group of men with hypogonadism and with a significant defect of gonad endocrinologic function. A similar phenomenon appeared in erythrocytes in a group of sexually mature rabbits after castration. In the course of substitutional treatment with testosterone esters given intramuscularly, the increase of activity characteristic for both examined glycolytic enzymes was observed in both experimental groups, i.e. the patients and the animals. The pyruvate kinase increase, however, was not statistically significant in the examined group of men, which resulted from the small size of the group. The authors suggest the existence of testosterone influence on regular activity of bone marrow glycolytic enzymes, and consequently on the mature erythrocytes. The decrease of aldolase and pyruvate kinase activity in erythrocytes of patients with male hypogonadism may decrease the erythrocytes valence. This ist another biochemical argument for the need of conducting long-term substitutional therapy in cases of male hypogonadism.

Hypokalemic myopathy associated with 17 alpha-hydroxylase deficiency: a case report.

We studied a patient with hypokalemic myopathy associated with 17 alpha-hydroxylase deficiency. An 18-year-old high school student, who appeared to be a girl with poorly developed secondary sex characteristics, had generalized muscle weakness. The cause of muscle weakness proved to be hypokalemic myopathy confirmed by clinical findings and muscle biopsy. Endocrinologic study demonstrated 17 alpha-hydroxylase deficiency with male pseudohermaphroditism. The metabolic abnormality of this patient was corrected by the administration of glucocorticoid. The possibility of this rare disease has to be considered when we examine a patient who has hypokalemic myopathy associated with hypogonadism.