Central University of the Caribbean

About: Central University of the Caribbean is a education organization based out in Bayamon, Puerto Rico, United States. It is known for research contribution in the topics: Population & Acquired immunodeficiency syndrome (AIDS). The organization has 460 authors who have published 617 publications receiving 11804 citations.

Downregulation of Kir4.1 inward rectifying potassium channel subunits by RNAi impairs potassium transfer and glutamate uptake by cultured cortical astrocytes.

Abstract: Glial cell-mediated potassium and glutamate homeostases play important roles in the regulation of neuronal excitability. Diminished potassium and glutamate buffering capabilities of astrocytes result in hyperexcitability of neurons and abnormal synaptic transmission. The role of the different K+ channels in maintaining the membrane potential and buffering capabilities of cortical astrocytes has not yet been definitively determined due to the lack of specific K+ channel blockers. The purpose of the present study was to assess the role of the inward-rectifying K+ channel subunit Kir4.1 on potassium fluxes, glutamate uptake and membrane potential in cultured rat cortical astrocytes using RNAi, whole-cell patch clamp and a colorimetric assay. The membrane potentials of control cortical astrocytes had a bimodal distribution with peaks at -68 and -41 mV. This distribution became unimodal after knockdown of Kir4.1, with the mean membrane potential being shifted in the depolarizing direction (peak at -45 mV). The ability of Kir4.1-suppressed cells to mediate transmembrane potassium flow, as measured by the current response to voltage ramps or sequential application of different extracellular [K+], was dramatically impaired. In addition, glutamate uptake was inhibited by knock-down of Kir4.1-containing channels by RNA interference as well as by blockade of Kir channels with barium (100 microM). Together, these data indicate that Kir4.1 channels are primarily responsible for significant hyperpolarization of cortical astrocytes and are likely to play a major role in potassium buffering. Significant inhibition of glutamate clearance in astrocytes with knock-down of Kir4.1 highlights the role of membrane hyperpolarization in this process.

Opposing effects of ubiquitin conjugation and SUMO modification of PCNA on replicational bypass of DNA lesions in Saccharomyces cerevisiae

Abstract: The Rad6-Rad18 ubiquitin-conjugating enzyme complex of Saccharomyces cerevisiae promotes replication through DNA lesions via three separate pathways that include translesion synthesis (TLS) by DNA polymerases zeta (Polzeta) and Poleta and postreplicational repair mediated by the Mms2-Ubc13 ubiquitin-conjugating enzyme and Rad5. Here we report our studies with a proliferating cell nuclear antigen (PCNA) mutation, pol30-119, which results from a change of the lysine 164 residue to arginine. It has been shown recently that following treatment of yeast cells with DNA-damaging agents, the lysine 164 residue of PCNA becomes monoubiquitinated in a Rad6-Rad18-dependent manner and that subsequently this PCNA residue is polyubiquitinated via a lysine 63-linked ubiquitin chain in an Mms2-Ubc13-, Rad5-dependent manner. PCNA is also modified by SUMO conjugation at the lysine 164 residue. Our genetic studies with the pol30-119 mutation show that in addition to conferring a defect in Polzeta-dependent UV mutagenesis and in Poleta-dependent TLS, this PCNA mutation inhibits postreplicational repair of discontinuities that form in the newly synthesized strand across from UV lesions. In addition, we provide evidence for the activation of the RAD52 recombinational pathway in the pol30-119 mutant and we infer that SUMO conjugation at the lysine 164 residue of PCNA has a role in suppressing the Rad52-dependent postreplicational repair pathway.

Rising Obesity Prevalence and Weight Gain Among Adults Starting Antiretroviral Therapy in the United States and Canada.

Abstract: The proportion of overweight and obese adults in the United States and Canada has increased over the past decade, but temporal trends in body mass index (BMI) and weight gain on antiretroviral therapy (ART) among HIV-infected adults have not been well characterized. We conducted a cohort study comparing HIV-infected adults in the North America AIDS Cohort Collaboration on Research and Design (NA-ACCORD) to United States National Health and Nutrition Examination Survey (NHANES) controls matched by sex, race, and age over the period 1998 to 2010. Multivariable linear regression assessed the relationship between BMI and year of ART initiation, adjusting for sex, race, age, and baseline CD4(+) count. Temporal trends in weight on ART were assessed using a generalized least-squares model further adjusted for HIV-1 RNA and first ART regimen class. A total of 14,084 patients from 17 cohorts contributed data; 83% were male, 57% were nonwhite, and the median age was 40 years. Median BMI at ART initiation increased from 23.8 to 24.8 kg/m(2) between 1998 and 2010 in NA-ACCORD, but the percentage of those obese (BMI ≥30 kg/m(2)) at ART initiation increased from 9% to 18%. After 3 years of ART, 22% of individuals with a normal BMI (18.5-24.9 kg/m(2)) at baseline had become overweight (BMI 25.0-29.9 kg/m(2)), and 18% of those overweight at baseline had become obese. HIV-infected white women had a higher BMI after 3 years of ART as compared to age-matched white women in NHANES (p = 0.02), while no difference in BMI after 3 years of ART was observed for HIV-infected men or non-white women compared to controls. The high prevalence of obesity we observed among ART-exposed HIV-infected adults in North America may contribute to health complications in the future.

New Insights on Astrocyte Ion Channels: Critical for Homeostasis and Neuron-Glia Signaling.

Abstract: Initial biophysical studies on glial cells nearly 50 years ago identified these cells as being electrically silent. These first studies also demonstrated a large K+ conductance, which led to the notion that glia may regulate extracellular K+ levels homeostatically. This view has now gained critical support from the study of multiple disease models discussed herein. Dysfunction of a major astrocyte K+ channel, Kir4.1, appears as an early pathological event underlying neuronal phenotypes in several neurodevelopmental and neurodegenerative diseases. An expanding list of other astrocyte ion channels, including the calcium-activated ion channel BEST-1, hemichannels, and two-pore domain K+ channels, all contribute to astrocyte biology and CNS function and underpin new forms of crosstalk between neurons and glia. Once considered merely the glue that holds the brain together, it is now increasingly recognized that astrocytes contribute in several fundamental ways to neuronal function. Emerging new insights and future perspectives of this active research area are highlighted within. SIGNIFICANCE STATEMENT The critical role of astrocyte potassium channels in CNS homeostasis has been reemphasized by recent studies conducted in animal disease models. Emerging evidence also supports the signaling role mediated by astrocyte ion channels such as BEST1, hemichannels, and two-pore channels, which enable astrocytes to interact with neurons and regulate synaptic transmission and plasticity. This minisymposium highlights recent developments and future perspectives of these research areas.