Gino Noris

Protein tyrosine phosphorylation in leukocyte activation through receptors for IgG.

Membrane receptors for the Fc portion of immunoglobulin G (IgG) antibodies (FcγRs) are expressed on almost every type of hematopoietic cells, where they mediate a wide variety of effector functions. A high degree of structural heterogeneity exists among FcγRs. The biological significance of such heterogeneity is unknown, since the structural diversity does not appear to be reflected in the binding specificity nor in the effector functions that each distinct receptor is able to mediate. Recent work has emphasized the essential role of protein tyrosine phosphorylation in the initiation of trans‐membrane signaling by these receptors. In this article we review the role of protein tyrosine phosphorylation in signal transduction by the different types of FcγRs in order to assess to what extent the structural heterogeneity of this receptor family is related to different activation pathways utilized by each of its members. J. Leukoc. Biol. 60: 433–440; 1996.

GABA inhibition of immortalized gonadotropin-releasing hormone neuronal excitability involves GABAA receptors negatively coupled to cyclic adenosine monophosphate formation

Abstractγ-Aminobutyric acid (GABA) has been implicated in the regulation of reproduction, particularly in the developmental modulation of gonadotropin-releasing hormone (GnRH) secretion. GnRH neurons are innervated by GABA-containing processes, and the administration of GABA stimulates and inhibits GnRH secretion in vivo and in vitro. We have previously shown that GABA can exert both of these actions in sequence, by acting directly on immortalized GnRH neurons. While the stimulation is the result of a GABAA receptor-mediated depolarization of the plasma membrane, the mechanism involved in the delayed inhibition is the subject of the present investigation. GABA (1 nM-10 µM) decreased the intracellular concentration of cyclic adenosine monophosphate (cAMP) in a dose- and time-dependent fashion. This effect was blocked by bicuculline and mimicked by muscimol but not by baclofen. To analyze the effect of GABA on cellular excitability, we used fura-2 loaded GT1-7 cells. Activation of voltage-sensitive calcium channels by high K+-induced depolarization (35 mM) increased [Ca2+]i. GABA (10µM) and muscimol (10 µM) reduced the amplitude of K+-induced [Ca2+]i transients. This inhibition was blocked by forskolin (20µM) or 8-Br-cAMP (1 mM). Altogether, these results show that GABAA receptors mediate a sustained inhibitory effect of GABA on GnRH neurons, and suggest the involvement of the cAMP pathway decreasing cellular excitability.

Androgen receptor CAG polymorphism and sporadic and early-onset prostate cancer among Mexican men.

A short CAG repeat length in the gene encoding for the androgen receptor (AR) has been associated with prostate cancer (PC) risk and aggressiveness. In Latino men, information on this association is scarce. Hence, the aim of this study was to evaluate this association in Mexican males. Using fragment analysis by capillary electrophoresis, we determined the number of CAG repeats—(CAG)n—in AR gene from 158 incident PC cases and 326 age-matched healthy controls (±5 years), residing in Mexico City, Mexico. According to Gleason scale and age at diagnosis, cases were classified as high (⩾7) and low grade (<7), as well as early onset (<60 years) or late onset PC (⩾60 years). At diagnosis, 78% of cases were classified as high-grade and 26.6% as early onset. Men with sporadic (no family history of PC) and early-onset PC presented shorter CAG repeat length than controls (18.6±2.2 vs 19.5±2.5; P=0.02). Lower number of CAG repeats (CAG)⩽19 were associated with a greater risk for early-onset PC (odds ratio: 2.31; 95% confidence interval: 1.14–4.69). CAG repeat length could increase the risk for sporadic and early-onset PC. The best cutoff point for identifying at-risk subjects was (CAG)19. However, further studies are necessary to replicate our findings in subjects with a family history of PC and also to evaluate the association between CAG repeats length and disease progression.

Association of vWA and TPOX Polymorphisms with Venous Thrombosis in Mexican Mestizos

Objective. Venous thromboembolism (VTE) is a multifactorial disorder and, worldwide, the most important cause of morbidity and mortality. Genetic factors play a critical role in its aetiology. Microsatellites are the most important source of human genetic variation having more phenotypic effect than many single nucleotide polymorphisms. Hence, we evaluate a possible relationship between VTE and the genetic variants in von Willebrand factor, human alpha fibrinogen, and human thyroid peroxidase microsatellites to identify possible diagnostic markers. Methods. Genotypes were obtained from 177 patients with VTE and 531 nonrelated individuals using validated genotyping methods. The allelic frequencies were compared; Bayesian methods were used to correct population stratification to avoid spurious associations. Results. The vWA-18, TPOX-9, and TPOX-12 alleles were significantly associated with VTE. Moreover, subjects bearing the combination vWA-18/TPOX-12 loci exhibited doubled risk for VTE (95% CI = 1.02–3.64), whereas the combination vWA-18/TPOX-9 showed an OR = 10 (95% CI = 4.93–21.49). Conclusions. The vWA and TPOX microsatellites are good candidate biomarkers in venous thromboembolism diseases and could help to elucidate their origins. Additionally, these polymorphisms could become useful markers for genetic studies of VTE in the Mexican population; however, further studies should be done owing that this data only show preliminary evidence.