scholarly journals Adult Leydig Cell Tumors of the Testis Caused by Germline Fumarate Hydratase Mutations

2006 ◽  
Vol 91 (8) ◽  
pp. 3071-3075 ◽  
Author(s):  
Luis G. Carvajal-Carmona ◽  
N. Afrina Alam ◽  
Patrick J. Pollard ◽  
Angela M. Jones ◽  
Ella Barclay ◽  
...  
Keyword(s):  
Leydig Cell ◽  
Cell Cancer ◽  
Fumarate Hydratase ◽  
Testicular Tumor ◽  
Wild Type ◽  
Guanine Nucleotide Binding Protein ◽  
Guanine Nucleotide Binding ◽  
Leydig Cell Tumors

Abstract Context: Leydig cell tumors (LCTs) are the most common non-germ-cell neoplasms of the testis. LCTs are often hormonally active and can result in precocious virilization or in adult feminization. We identified an LCT in an affected individual from a kindred with hereditary leiomyomatosis and renal cell cancer (HLRCC) and a germline fumarate hydratase (FH) mutation (N64T). Objective: Our objective was to investigate the role of FH mutations in predisposition to LCTs. Design: We tested for pathogenic effects of the N64T mutation and screened an additional 29 unselected adult LCTs for FH alterations. We also tested these LCTs for mutations in two genes, the LH/choriogonadotropin receptor (LHCGR) and the guanine nucleotide-binding protein α (GNAS) that had been implicated in LCT tumorigenesis. Results: No mutations were found in GNAS, and one tumor had a LHCGR somatic substitution. In addition to the HLRCC case with the N64T germline FH mutation, we identified one other LCT with a previously unreported FH mutation (M411I). Both LCTs from these patients showed loss of the wild-type FH allele. Immunohistochemical and in situ hybridization analyses demonstrated activation of the hypoxia/angiogenesis pathway not only in the tumors belonging to the FH mutation carriers but also in several other mutation-negative LCTs. Conclusions: Our study shows that some LCTs are caused by FH mutations and represents one of the first reports of germline mutations in any type of adult testicular tumor.

scholarly journals The role of palmitoylation of the guanine nucleotide binding protein G11α in defining interaction with the plasma membrane

1995 ◽  
Vol 310 (3) ◽  
pp. 1021-1027 ◽  
Author(s):  
J F McCallum ◽  
A Wise ◽  
M A Grassie ◽  
A I Magee ◽  
F Guzzi ◽  
...  
Keyword(s):  
Double Mutant ◽  
Sodium Cholate ◽  
Particulate Fraction ◽  
Wild Type ◽  
Guanine Nucleotide Binding Protein ◽  
Sds Page ◽  
Exclusion Chromatography ◽  
Resistant Mutants ◽  
Guanine Nucleotide Binding

Mutations of Cys-9 to serine, Cys-10 to serine and a combination of both alterations were produced in a cDNA encoding murine G11 alpha to potentially interfere with the ability of the expressed polypeptides to act as substrates for post-translational palmitoylation. Each of these mutants and the wild-type protein were expressed in simian COS-1 cells. Mutation of either cysteine-9 or cysteine-10 decreased the degree of palmitoylation of the protein by some 80% compared with the wild-type, while the double mutant totally failed to incorporate [3H]palmitate. By contrast, in all transfections the endogenously expressed simian G11 alpha incorporated [3H]palmitate to similar levels. Particulate and cytoplasmic fractions from these cells were subjected to SDS/PAGE under conditions which allow resolution of primate and rodent forms of G11 alpha. Immunoblotting of these fractions demonstrated that in all cases the endogenously expressed simian G11 alpha was exclusively associated with the particulate fraction, as was the transfected and expressed wild-type murine G11 alpha. By contrast, each of the mutated forms of murine G11 alpha displayed a distribution in which approx. 70% of the expressed protein was present in the particulate fraction and 30% in the supernatant. To examine the conformation of the particulate expressed forms of murine G11 alpha, these fractions were treated with various concentrations of sodium cholate and immunoblots were subsequently performed on the solubilized and remaining particulate proteins. Whereas essentially all of the endogenous simian G11 alpha was solubilized by treatment with 1% (w/v) sodium cholate and some 50% with 0.32% cholate, expressed wild-type murine G11 alpha was more recalcitrant to solubilization. However, that fraction of wild-type murine G11 alpha which was solubilized behaved identically to the endogenous simian G11 alpha on Superose-12 gel-exclusion chromatography. The particulate fraction of the C9S/C10S double mutant of murine G11 alpha was highly resistant to solubilization by sodium cholate, whereas the particulate fractions of the two single cysteine to serine mutants were intermediate to the wild-type and double mutant in their ability to be solubilized by this detergent. These data demonstrate that the palmitoylation status of the cysteine residues at positions 9 and 10 in murine G11 alpha plays a central role in defining membrane association of this G-protein and indicate that much of the particulate fraction of the expressed palmitoylation-resistant mutants is likely to represent non-functional rather than correctly folded protein.(ABSTRACT TRUNCATED AT 400 WORDS)

Tonic inhibition of renal response to vasopressin by a pertussis toxin substrate

1988 ◽  
Vol 255 (6) ◽  
pp. F1107-F1115
Author(s):  
W. B. Jeffries ◽  
R. Fallet ◽  
G. D. Gong ◽  
P. Van Dreal ◽  
W. A. Pettinger
Keyword(s):  
Camp Accumulation ◽  
Guanine Nucleotide Binding Protein ◽  
Renal Response ◽  
Collecting Tubule ◽  
Adenylate Cyclase Stimulation ◽  
V2 Receptor ◽  
Guanine Nucleotide Binding

The putative role of the inhibitory guanine nucleotide binding protein (Gi) in modulating the renal response to vasopressin was investigated using islet activating protein (IAP). IAP treatment in rats in vivo abolished the capacity of alpha 2-adrenoceptors to reverse vasopressin-induced adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in microdissected cortical collecting tubule (CCT) segments. IAP pretreatment also caused a marked upward shift in the dose-response curve of vasopressin (10(-10) to 10(-4) M)-induced cAMP accumulation. Augmentation of the response to vasopressin in rat CCT was dependent on the in vivo dose of IAP and paralleled the loss in alpha 2-adrenoceptor responsiveness. In the isolated perfused kidney the antinatriuretic and antidiuretic effects of the V2-receptor agonist desamino-8-D-arginine vasopressin (DDAVP) (1 pM) were enhanced following IAP pretreatment. alpha 2-Adrenoceptor stimulation (30 nM epinephrine) inhibited the renal effects of DDAVP (1 pM) in kidneys from control but not IAP-pretreated rats. Interestingly, IAP pretreatment alone caused increased urine flow rate and enhanced excretion of sodium and chloride without affecting potassium excretion or renal hemodynamics in vitro. Our results suggest that an IAP substrate, probably Gi, 1) is required for signal transduction by renal alpha 2-adrenoceptors, 2) may tonically modulate the response to vasopressin in the CCT but not of parathyroid hormone in the proximal convoluted tubule, and 3) participates in renal water and electrolyte reabsorption independent of exogenous adenylate cyclase stimulation.

Mechanism of proximal tubule bicarbonate absorption in NHE3 null mice

1999 ◽  
Vol 277 (2) ◽  
pp. F298-F302 ◽  
Author(s):  
Tong Wang ◽  
Chao-Ling Yang ◽  
Thecla Abbiati ◽  
Patrick J. Schultheis ◽  
Gary E. Shull ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Proximal Tubule ◽  
Apical Membrane ◽  
Significant Inhibition ◽  
Fluid Absorption ◽  
Wild Type ◽  
Significant Component ◽  
Nhe Isoforms

NHE3 is the predominant isoform responsible for apical membrane Na+/H+exchange in the proximal tubule. Deletion of NHE3 by gene targeting results in an NHE3−/−mouse with greatly reduced proximal tubule[Formula: see text] absorption compared with NHE3+/+ animals (P. J. Schultheis, L. L. Clarke, P. Meneton, M. L. Miller, M. Soleimani, L. R. Gawenis, T. M. Riddle, J. J. Duffy, T. Doetschman, T. Wang, G. Giebisch, P. S. Aronson, J. N. Lorenz, and G. E. Shull. Nature Genet. 19: 282–285, 1998). The purpose of the present study was to evaluate the role of other acidification mechanisms in mediating the remaining component of proximal tubule [Formula: see text] reabsorption in NHE3−/− mice. Proximal tubule transport was studied by in situ microperfusion. Net rates of[Formula: see text] ( J HCO3) and fluid absorption ( J v) were reduced by 54 and 63%, respectively, in NHE3 null mice compared with controls. Addition of 100 μM ethylisopropylamiloride (EIPA) to the luminal perfusate caused significant inhibition of J HCO3 and J v in NHE3+/+ mice but failed to inhibit J HCO3 or J v in NHE3−/− mice, indicating lack of activity of NHE2 or other EIPA-sensitive NHE isoforms in the null mice. Addition of 1 μM bafilomycin caused a similar absolute decrement in J HCO3 in wild-type and NHE3 null mice, indicating equivalent rates of[Formula: see text] absorption mediated by H+-ATPase. Addition of 10 μM Sch-28080 did not reduce J HCO3 in either wild-type or NHE3 null mice, indicating lack of detectable H+-K+-ATPase activity in the proximal tubule. We conclude that, in the absence of NHE3, neither NHE2 nor any other EIPA-sensitive NHE isoform contributes to mediating [Formula: see text] reabsorption in the proximal tubule. A significant component of[Formula: see text] reabsorption in the proximal tubule is mediated by bafilomycin-sensitive H+-ATPase, but its activity is not significantly upregulated in NHE3 null mice.

Metalloprotease cleavage of the N terminus of the orphan G protein–coupled receptor GPR37L1 reduces its constitutive activity

2016 ◽  
Vol 9 (423) ◽  
pp. ra36-ra36 ◽  
Author(s):  
James L. J. Coleman ◽  
Tony Ngo ◽  
Johannes Schmidt ◽  
Nadine Mrad ◽  
Chu Kong Liew ◽  
...  
Keyword(s):  
G Protein ◽  
Cultured Cells ◽  
Amino Terminus ◽  
Wild Type ◽  
Guanine Nucleotide Binding Protein ◽  
Inactive Form ◽  
In The Wild ◽  
Reporter Assays ◽  
Guanine Nucleotide Binding ◽  
G Protein Coupled

Little is known about the pharmacology or physiology of GPR37L1, a G protein (heterotrimeric guanine nucleotide–binding protein)–coupled receptor that is abundant in the cerebellum. Mice deficient in this receptor exhibit precocious cerebellar development and hypertension. We showed that GPR37L1 coupled to the G protein Gαs when heterologously expressed in cultured cells in the absence of any added ligand, whereas a mutant receptor that lacked the amino terminus was inactive. Conversely, inhibition of ADAMs (a disintegrin and metalloproteases) enhanced receptor activity, indicating that the presence of the amino terminus is necessary for GPR37L1 signaling. Metalloprotease-dependent processing of GPR37L1 was evident in rodent cerebellum, where we detected predominantly the cleaved, inactive form. However, comparison of the accumulation of cAMP (adenosine 3′,5′-monophosphate) in response to phosphodiesterase inhibition in cerebellar slice preparations from wild-type and GPR37L1-null mice showed that some constitutive signaling remained in the wild-type mice. In reporter assays of Gαs or Gαi signaling, the synthetic, prosaposin-derived peptide prosaptide (TX14A) did not increase GPR37L1 activity. Our data indicate that GPR37L1 may be a constitutively active receptor, or perhaps its ligand is present under the conditions that we used for analysis, and that the activity of this receptor is instead controlled by signals that regulate metalloprotease activity in the tissue.

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