Lysophosphatidic acid LPA1-3 receptors: signaling, regulation and in silico analysis of their putative phosphorylation sites

Lysophosphatidic acid (LPA) is a bioactive lipid with a plethora of roles in the normal function of our organism as well as in the pathogenesis of many diseases. The actions of LPA are mainly mediated through a family of G protein-coupled receptors, which currently is composed of six members; other receptors might participate in LPA actions including a nuclear receptor. In this work, we mainly focus on three of these receptors, i. e.,  LPA1-3; those that were initially discovered which, have been more extensively studied and that are phylogenetically related among themselves,  as well as with receptors for other bioactive phospholipids, such as those for spingosine 1-phosphate.  The characteristics of these receptors, their patterns of tissue expression, and some of the actions in which they are involved are presented. Regulation of receptor function, including desensitization, internalization and phosphorylation has only been studied for the LPA1 subtype. However, in silico analysis of potential phosphorylation sites indicate that all of these three receptors are putatively regulated by agonist activation and heterologous stimuli. We think LPA1-3 receptor regulation constitutes a niche of investigation that is potentially of great importance considering the physiological and pathophysiological actions in which they are involved.&nbsp

Nitrogen and Phosphorous Retention in Tropical Eutrophic Reservoirs with Water Level Fluctuations: A Case Study Using Mass Balances on a Long-Term Series

Nitrogen and phosphorous loading drives eutrophication of aquatic systems. Lakes and reservoirs are often effective N and P sinks, but the variability of their biogeochemical dynamics is still poorly documented, particularly in tropical systems. To contribute to the extending of information on tropical reservoirs and to increase the insight on the factors affecting N and P cycling in aquatic ecosystems, we here report on a long-term N and P mass balance (2003–2018) in Valle de Bravo, Mexico, which showed that this tropical eutrophic reservoir lake acts as a net sink of N (−41.7 g N m y) and P (−2.7 g P m y), mainly occurring through net sedimentation, equivalent to 181% and 68% of their respective loading (23.0 g N m y and 4.2 g P m y). The N mass balance also showed that the Valle de Bravo reservoir has a high net N atmospheric influx (31.6 g N m y), which was 1.3 times the external load and likely dominated by N fixation. P flux was driven mainly by external load, while in the case of N, net fixation also contributed. During a period of high water level fluctuations, the net N atmospheric flux decreased by 50% compared to high level years. Our results outlining water regulation can be used as a useful management tool of water bodies, by decreasing anoxic conditions and net atmospheric fluxes, either through decreasing nitrogen fixation and/or promoting denitrification and other microbial processes that alleviate the N load. These findings also sustain the usefulness of long-term mass balances to assess biogeochemical dynamics and its variability.This research was funded by UNAM, PAPIIT-IN207702 and CONACYT-SEMARNAT, C01-1125 projects to M.M-

Izaña Atmospheric Research Center. Activity Report 2019-2020

Editors: Emilio Cuevas, Celia Milford and Oksana Tarasova.[EN]The Izaña Atmospheric Research Center (IARC), which is part of the State Meteorological Agency of Spain (AEMET), is a site of excellence in atmospheric science. It manages four observatories in Tenerife including the high altitude Izaña Atmospheric Observatory. The Izaña Atmospheric Observatory was inaugurated in 1916 and since that date has carried out uninterrupted meteorological and climatological observations, contributing towards a unique 100-year record in 2016. This reports are a summary of the many activities at the Izaña Atmospheric Research Center to the broader community. The combination of operational activities, research and development in state-of-the-art measurement techniques, calibration and validation and international cooperation encompass the vision of WMO to provide world leadership in expertise and international cooperation in weather, climate, hydrology and related environmental issues.[ES]El Centro de Investigación Atmosférica de Izaña (CIAI), que forma parte de la Agencia Estatal de Meteorología de España (AEMET), representa un centro de excelencia en ciencias atmosféricas. Gestiona cuatro observatorios en Tenerife, incluido el Observatorio de Izaña de gran altitud, inaugurado en 1916 y que desde entonces ha realizado observaciones meteorológicas y climatológicas ininterrumpidas y se ha convertido en una estación centenaria de la OMM. Estos informes resumen las múltiples actividades llevadas a cabo por el Centro de Investigación Atmosférica de Izaña. El liderazgo del Centro en materia de investigación y desarrollo con respecto a las técnicas de medición, calibración y validación de última generación, así como la cooperación internacional, le han otorgado una reputación sobresaliente en lo que se refiere al tiempo, el clima, la hidrología y otros temas ambientales afines

Lysophosphatidic acid LPA1-3 receptors: signaling, regulation and in silico analysis of their putative phosphorylation sites

Lysophosphatidic acid (LPA) is a bioactive lipid with a plethora of roles in the normal function of our organism as well as in the pathogenesis of many diseases. The actions of LPA are mainly mediated through a family of G protein-coupled receptors, which currently is composed of six members; other receptors might participate in LPA actions including a nuclear receptor. In this work, we mainly focus on three of these receptors, i. e.,  LPA1-3; those that were initially discovered which, have been more extensively studied and that are phylogenetically related among themselves,  as well as with receptors for other bioactive phospholipids, such as those for spingosine 1-phosphate.  The characteristics of these receptors, their patterns of tissue expression, and some of the actions in which they are involved are presented. Regulation of receptor function, including desensitization, internalization and phosphorylation has only been studied for the LPA1 subtype. However, in silico analysis of potential phosphorylation sites indicate that all of these three receptors are putatively regulated by agonist activation and heterologous stimuli. We think LPA1-3 receptor regulation constitutes a niche of investigation that is potentially of great importance considering the physiological and pathophysiological actions in which they are involved.&nbsp

Novel Structural Approaches to Study GPCR Regulation

Background: Upon natural agonist or pharmacological stimulation, G protein-coupled receptors (GPCRs) are subjected to posttranslational modifications, such as phosphorylation and ubiquitination. These posttranslational modifications allow protein–protein interactions that turn off and/or switch receptor signaling as well as trigger receptor internalization, recycling or degradation, among other responses. Characterization of these processes is essential to unravel the function and regulation of GPCR. Methods: In silico analysis and methods such as mass spectrometry have emerged as novel powerful tools. Both approaches have allowed proteomic studies to detect not only GPCR posttranslational modifications and receptor association with other signaling macromolecules but also to assess receptor conformational dynamics after ligand (agonist/antagonist) association. Results: this review aims to provide insights into some of these methodologies and to highlight how their use is enhancing our comprehension of GPCR function. We present an overview using data from different laboratories (including our own), particularly focusing on free fatty acid receptor 4 (FFA4) (previously known as GPR120) and α1A- and α1D-adrenergic receptors. From our perspective, these studies contribute to the understanding of GPCR regulation and will help to design better therapeutic agents

Phosphorylation and Internalization of Lysophosphatidic Acid Receptors LPA1, LPA2, and LPA3.

The lysophosphatidic acid receptors LPA1, LPA2, and LPA3 were individually expressed in C9 cells and their signaling and regulation were studied. Agonist-activation increases intracellular calcium concentration in a concentration-dependent fashion. Phorbol myristate acetate markedly inhibited LPA1- and LPA3-mediated effect, whereas that mediated by LPA2 was only partially diminished; the actions of the phorbol ester were inhibited by bisindolylmaleimide I and by overnight incubation with the protein kinase C activator, which leads to down regulation of this protein kinase. Homologous desensitization was also observed for the three LPA receptors studied, with that of LPA2 receptors being consistently of lesser magnitude; neither inhibition nor down-regulation of protein kinase C exerted any effect on homologous desensitization. Activation of LPA1-3 receptors induced ERK 1/2 phosphorylation; this effect was markedly attenuated by inhibition of epidermal growth factor receptor tyrosine kinase activity, suggesting growth factor receptor transactivation in this effect. Lysophosphatidic acid and phorbol myristate acetate were able to induce LPA1-3 phosphorylation, in time- and concentration-dependent fashions. It was also clearly observed that agonists and protein kinase C activation induced internalization of these receptors. Phosphorylation of the LPA2 subtype required larger concentrations of these agents and its internalization was less intense than that of the other subtypes.Our data show that these three LPA receptors are phosphoproteins whose phosphorylation state is modulated by agonist-stimulation and protein kinase C-activation and that differences in regulation and cellular localization exist, among the subtypes

Effect of LPA on intracellular calcium concentration ([Ca²⁺]_i).

<p>Wild type C9 cells (panel A) or overexpressing LPA₁ (panel B), LPA₂ (panel C) or LPA₃ (panel D) were stimulated by different concentrations of LPA. Plotted are the increases in intracellular calcium as mean ± S. E. M. of 4–5 experiments using different cell preparations.</p

Time-courses of the effects of LPA and PMA on LPA_1–3 receptor phosphorylation.

<p>Cells overexpressing LPA₁ (black, circles), LPA₂ (blue, squares) or LPA₃ (red, triangles) receptors were incubated for the times indicated in the presence of 1 μM LPA (Panel A) or 1 μM PMA (Panel B). Plotted are the percentage of baseline phosphorylations as mean ± S. E. M. of 4–5 experiments using different cell preparations. Representative autoradiographs are presented for the different receptor subtypes.</p

Effect of LPA on ERK 1/2 phosphorylation.

<p>Cells overexpressing LPA₁ (black, circles), LPA₂ (blue, squares) or LPA₃ (red, triangles) receptors were incubated for the times indicated in the presence of 1 μM LPA, incubation was terminated and phospho-ERK 1/2 (pERK) and total ERK 1/2 (ERK) were assayed by Western blotting. Plotted are the increases in phospho-ERK 1/2 as mean ± S. E. M. of 4–5 experiments using different cell preparations. Representative Western blots are presented for the different receptor subtypes.</p

Concentration-response curves to LPA and PMA on LPA_1–3 receptor phosphorylation.

<p>Cells overexpressing LPA₁ (black, circles), LPA₂ (blue, squares) or LPA₃ (red, triangles) receptors were incubated for 15 min in the presence of different concentrations of LPA (Panel A) or PMA (Panel B). Plotted are the percentage of baseline phosphorylations as mean ± S. E. M. of 4–5 experiments using different cell preparations. Representative autoradiographs are presented for the different receptor subtypes.</p