OCaR1 endows exocytic vesicles with autoregulatory competence by preventing uncontrolled Ca2+ release, exocytosis, and pancreatic tissue damage.

Regulated exocytosis is initiated by increased Ca2+ concentrations in close spatial proximity to secretory granules, which is effectively prevented when the cell is at rest. Here we showed that exocytosis of zymogen granules in acinar cells was driven by Ca2+ directly released from acidic Ca2+ stores including secretory granules through NAADP-activated two-pore channels (TPCs). We identified OCaR1 (encoded by Tmem63a) as an organellar Ca2+ regulator protein integral to the membrane of secretory granules that controlled Ca2+ release via inhibition of TPC1 and TPC2 currents. Deletion of OCaR1 led to extensive Ca2+ release from NAADP-responsive granules under basal conditions as well as upon stimulation of GPCR receptors. Moreover, OCaR1 deletion exacerbated the disease phenotype in murine models of severe and chronic pancreatitis. Our findings showed OCaR1 as a gatekeeper of Ca2+ release that endows NAADP-sensitive secretory granules with an autoregulatory mechanism preventing uncontrolled exocytosis and pancreatic tissue damage.

Trophectoderm cell failure leads to peri-implantation lethality in Trpm7-deficient mouse embryos.

Early embryogenesis depends on proper control of intracellular homeostasis of ions including Ca2+ and Mg2+. Deletion of the Ca2+ and Mg2+ conducting the TRPM7 channel is embryonically lethal in mice but leaves compaction, blastomere polarization, blastocoel formation, and correct specification of the lineages of the trophectoderm and inner cell mass unaltered despite that free cytoplasmic Ca2+ and Mg2+ is reduced at the two-cell stage. Although Trpm7-/- embryos are able to hatch from the zona pellucida, no expansion of Trpm7-/- trophoblast cells can be observed, and Trpm7-/- embryos are not identifiable in utero at E6.5 or later. Given the proliferation and adhesion defect of Trpm7-/- trophoblast stem cells and the ability of Trpm7-/- ESCs to develop to embryos in tetraploid embryo complementation assays, we postulate a critical role of TRPM7 in trophectoderm cells and their failure during implantation as the most likely explanation of the developmental arrest of Trpm7-deficient mouse embryos.

Contribution of human esterases to the metabolism of selected drugs of abuse.

Human esterases such as the human carboxylesterases (hCES) are important for the catalytic ester hydrolysis of xenobiotics and they play an important role in the detoxification of drugs (e.g., cocaine) but also in the activation of prodrugs (e.g., ramipril). Therefore, the aim of the presented study was to characterize the enzyme-catalyzed ester hydrolysis of ten drugs (cocaine, dimethocaine, ethylphenidate, 4-fluoro-3α-tropacocaine, 4-fluoro-3ß-tropacocaine, heroin, methylphenidate, mitragynine, ramipril, and thebacon) by different esterase-containing systems (recombinant hCES1b, hCES1c, and hCES2, pooled human liver microsomes, pooled human liver S9 fraction, and pooled human plasma). Michaelis-Menten kinetic studies were done using in vitro incubations with the aforementioned enzyme-containing systems and LC coupled to ion trap MS for analysis. Ramipril and heroin were used as known model substrates to ensure reliable incubation conditions. The hydrolysis reactions followed classic Michaelis-Menten kinetics with exception of cocaine and 4-fluoro-3α-tropacocaine, for which hydrolysis rate was too low for reliable modeling. The substrates were mainly metabolized by the following enzymes systems: cocaine, hCES1c; dimethocaine, human plasma esterases; ethylphenidate, hCES1c; 4-fluoro-3ß-tropacocaine, human plasma esterases; heroin, hCES2; methylphenidate, hCES1c; mitragynine, hCES1c; ramipril, hCES1b; thebacon, hCES2. Compounds bearing a small alcohol part and a larger acyl part showed higher affinity to hCES1 while those with a large alcohol part showed higher affinity to hCES2. The collected data are important for prediction of drug-drug or drug-food interactions as well as for individual variations in metabolism of drugs of abuse due to enzyme polymorphisms.

Análise sialométrica em indivíduos portadores da síndrome de Down / Sialometric assessment of individuals with Down

A síndrome de Down (SD) é a alteração cromossômica mais comum no ser humano e caracteriza-se pelo aparecimento de um cromossomo extra, localizado no par 21. Objetivo: Nesta pesquisa estudou-se a velocidade de fluxo, o pH e a capacidade de tamponamento salivar em pacientes portadores da síndrome de Down. Materiais e Métodos: Foram selecionados 60 indivíduos não aparentados, pareados em idade e sexo, residentes em Curitiba, Paraná, sendo 30 indivíduos diagnosticados com SD (grupo experimental) e 30 indivíduos normorreativos (grupo controle). Para as avaliações bioquímicas salivares coletaram-se as amostras pelo método Spitting preconizado por Navazesh (1992) e posteriormente realizaram-se as análises. O fluxo salivar foi calculado através da fórmula de Banderas-Tarabay (1997). O pH salivar foi mensurado com o auxílio de um medidor digital e a capacidade tampão com o kit Caritest® – SL. Resultados: O valor médio do fluxo salivar foi estatisticamente menor para os indivíduos portadores da SD e os valores médios de pH e capacidade tampão salivar não diferiram entre os grupos. Conclusão: Indivíduos com SD apresentaram alterações uantitativas e não qualitativas do fluido salivar...

Down syndrome (DS) is the most common chromosomal abnormality in humans and is characterizedby the appearance of an extra chromosome, located at par 21. Objective: In this research we studiedthe flow rate, pH and buffering capacity of saliva in patients with Down syndrome. Materials and methods:60 unrelated individuals were selected matched by age and sex, living in Curitiba, Paraná, with 30 patientsdiagnosed with DS (experimental group) and 30 normoreactive individuals (control group). For biochemicalassessment, salivary samples were collected by Spitting method, recommended by Navazesh (1992) and thenthe analyses were carried out. Salivary flow was calculated using the formula of Banderas-Tarabay (1997).Salivary pH was measured with the aid of a digital meter and buffering capacity with the Caritest® – SL kit.Results: The mean salivary flow was statistically lower for patients with SD and the average values of pH andsalivary buffer capacity did not differ between groups. Conclusion: Individuals with SD showed no quantitativeand qualitative changes in salivary fluid...