Divergent calcium signaling in RBCs from Tropidurus torquatus (Squamata – Tropiduridae) strengthen classification in lizard evolution

Abstract\ud \ud \ud \ud Background\ud \ud We have previously reported that a Teiid lizard red blood cells (RBCs) such as Ameiva ameiva and Tupinambis merianae controls intracellular calcium levels by displaying multiple mechanisms. In these cells, calcium stores could be discharged not only by: thapsigargin, but also by the Na+/H+ ionophore monensin, K+/H+ ionophore nigericin and the H+ pump inhibitor bafilomycin as well as ionomycin. Moreover, these lizards possess a P2Y-type purinoceptors that mobilize Ca2+ from intracellular stores upon ATP addition.\ud \ud \ud \ud Results\ud \ud Here we report, that RBCs from the tropidurid lizard Tropidurus torquatus store Ca2+ in endoplasmic reticulum (ER) pool but unlike in the referred Teiidae, these cells do not store calcium in monensin-nigericin sensitive pools. Moreover, mitochondria from T. torquatus RBCs accumulate Ca2+. Addition of ATP to a calcium-free medium does not increase the [Ca2+]c levels, however in a calcium medium we observe an increase in cytosolic calcium. This is an indication that purinergic receptors in these cells are P2X-like.\ud \ud \ud \ud Conclusion\ud \ud T. torquatus RBCs present different mechanisms from Teiid lizard red blood cells (RBCs), for controlling its intracellular calcium levels. At T. torquatus the ion is only stored at endoplasmic reticulum and mitochondria. Moreover activation of purinergic receptor, P2X type, was able to induce an influx of calcium from extracelullar medium. These studies contribute to the understanding of the evolution of calcium homeostasis and signaling in nucleated RBCs.We thank Fundação de Amparo à Pesquisa de São Paulo (FAPESP) for funding CRSG. FHB received fellowship from FAPESP. We thank Robson Sartorello and Miguel T. Rodrigues for collecting the lizards.We thank Fundação de Amparo à Pesquisa de São Paulo (FAPESP) for funding CRSG. FHB received fellowship from FAPESP. We thank Robson Sartorello and Miguel T. Rodrigues for collecting the lizards

Cyclic AMP and calcium interplay as second messengers in melatonin-dependent regulation of Plasmodium falciparum cell cycle

The host hormone melatonin increases cytoplasmic Ca2+ concentration and synchronizes Plasmodium cell cycle (Hotta, C.T., M.L. Gazarini, F.H. Beraldo, F.P. Varotti, C. Lopes, R.P. Markus, T. Pozzan, and C.R. Garcia. 2000. Nat. Cell Biol. 2:466–468). Here we show that in Plasmodium falciparum melatonin induces an increase in cyclic AMP (cAMP) levels and cAMP-dependent protein kinase (PKA) activity (40 and 50%, respectively)

Camobilization in Fluo-3-labelled RBCs of the lizard : A) RBCs incubated in calcium medium (1 mM CaCl) were treated where indicated with the SERCA inhibitor, thapsigargin (5 μM)

<p><b>Copyright information:</b></p><p>Taken from "Divergent calcium signaling in RBCs from (Squamata – Tropiduridae) strengthen classification in lizard evolution"</p><p>http://www.biomedcentral.com/1472-6793/7/7</p><p>BMC Physiology 2007;7():7-7.</p><p>Published online 23 Aug 2007</p><p>PMCID:PMC2018699.</p><p></p> as in A, but CaClwas omitted and the medium was supplemented with 15 mM EGTA THG (5 μM) was add before addition of Caionophore ionomycin (10 μM). C) Effect of THG (5 μM) in RBC pre incubated with ionomycin (10 μM). D) Monensin (25 μM) was not able to induce an intracellular Caincrease

Increase of mitochondrial Capromotes an increase of NADPH in RBCs loaded with mitochondrial CaRhod-2

<p><b>Copyright information:</b></p><p>Taken from "Divergent calcium signaling in RBCs from (Squamata – Tropiduridae) strengthen classification in lizard evolution"</p><p>http://www.biomedcentral.com/1472-6793/7/7</p><p>BMC Physiology 2007;7():7-7.</p><p>Published online 23 Aug 2007</p><p>PMCID:PMC2018699.</p><p></p> A) Increase of mitochondrial Ca[Ca]and fluorescence of NADPH induced by ATP (50 μM) in RBCs loaded with Rhod-2 AM, in the Camedium. B) similar experiments in a Cafree medium C) Ionomycin (10 μM) promotes a increase of [Ca]with concomitant increase of NADPH fluorescence