Ectocellular CD38-catalyzed synthesis and intracellular Ca2+-signalling activity of cyclic ADP-ribose in T-lymphocytes are not functionally related.

AbstractCyclic ADP-ribose (cADPR) is a natural metabolite of β-NAD+ with a potent Ca2+-mobilizing activity in different cell types, including T-lymphocytes. We investigated (i) whether stimulation of T-lymphocytes with different agonists affects the intracellular concentration of cADPR, and (ii) whether the lymphocyte antigen CD38, through its ectocellular ADP-ribosyl cyclase and cADPR-hydrolase enzymatic activities, can account for the regulation of the intracellular levels of cADPR and the Ca2+-mobilizing effects of this nucleotide in Jurkat and HPB.ALL T-lymphocytes. The anti-CD3 antibody OKT3, the sphingolipid sphingosine and lysophosphatidic acid induced an increase in intracellular cADPR with concomitant increases in the intracellular Ca2+ concentration ([Ca2+]i). In contrast, activation of an ectocellular ADP-ribosyl cyclase by preincubation of cells with β-NAD+ led to a dose-dependent increase in cADPR, but no changes in [Ca2+]i were observed. However, extensive washing of the cells following preincubation with NAD+ demonstrated that the increases in cADPR were not intracellular but due to cell surface-associated nucleotide. Accordingly, measurements of ADP-ribosyl cyclase activity in intact T-cells showed ectocellular synthesis of cADPR, but no evidence was obtained for a shift of this activity into the cells which could account for intracellular accumulation of cADPR. Taken together, the results indicate no direct involvement of the ADP-ribosyl cyclase activity of CD38 on the regulation of the cADPR-mediated intracellular Ca2+-signalling in T-lymphocytes

Microorganism Response to Stressed Terrestrial Environments: A Raman Spectroscopic Perspective of Extremophilic Life Strategies

Raman spectroscopy is a valuable analytical technique for the identification of biomolecules and minerals in natural samples, which involves little or minimal sample manipulation. In this paper, we evaluate the advantages and disadvantages of this technique applied to the study of extremophiles. Furthermore, we provide a review of the results published, up to the present point in time, of the bio- and geo-strategies adopted by different types of extremophile colonies of microorganisms. We also show the characteristic Raman signatures for the identification of pigments and minerals, which appear in those complex samples