PP2A/B56 and GSK3/Ras suppress PKB activity during Dictyostelium chemotaxis

We have previously shown that the Dictyostelium protein phosphatase 2A regulatory subunit B56, encoded by psrA, modulates Dictyostelium cell differentiation through negatively affecting glycogen synthase kinase 3 (GSK3) function. Our follow-up research uncovered that B56 preferentially associated with GDP forms of RasC and RasD, but not with RasG in vitro, and psrA− cells displayed inefficient activation of multiple Ras species, decreased random motility, and inefficient chemotaxis toward cAMP and folic acid gradient. Surprisingly, psrA− cells displayed aberrantly high basal and poststimulus phosphorylation of Dictyostelium protein kinase B (PKB) kinase family member PKBR1 and PKB substrates. Expression of constitutively active Ras mutants or inhibition of GSK3 in psrA− cells increased activities of both PKBR1 and PKBA, but only the PKBR1 activity was increased in wild-type cells under the equivalent conditions, indicating that either B56- or GSK3-mediated suppressive mechanism is sufficient to maintain low PKBA activity, but both mechanisms are necessary for suppressing PKBR1. Finally, cells lacking RasD or RasC displayed normal PKBR1 regulation under GSK3-inhibiting conditions, indicating that RasC or RasD proteins are essential for GSK3-mediated PKBR1 inhibition. In summary, B56 constitutes inhibitory circuits for PKBA and PKBR1 and thus heavily affects Dictyostelium chemotaxis

Phosphorylation-dependent inhibition of Cdc42 GEF Gef1 by 14-3-3 protein Rad24 spatially regulates Cdc42 GTPase activity and oscillatory dynamics during cell morphogenesis

© The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Molecular Biology of the Cell 26 (2015): 3520-3534, doi:10.1091/mbc.E15-02-0095.Active Cdc42 GTPase, a key regulator of cell polarity, displays oscillatory dynamics that are anticorrelated at the two cell tips in fission yeast. Anticorrelation suggests competition for active Cdc42 or for its effectors. Here we show how 14-3-3 protein Rad24 associates with Cdc42 guanine exchange factor (GEF) Gef1, limiting Gef1 availability to promote Cdc42 activation. Phosphorylation of Gef1 by conserved NDR kinase Orb6 promotes Gef1 binding to Rad24. Loss of Rad24–Gef1 interaction increases Gef1 protein localization and Cdc42 activation at the cell tips and reduces the anticorrelation of active Cdc42 oscillations. Increased Cdc42 activation promotes precocious bipolar growth activation, bypassing the normal requirement for an intact microtubule cytoskeleton and for microtubule-dependent polarity landmark Tea4-PP1. Further, increased Cdc42 activation by Gef1 widens cell diameter and alters tip curvature, countering the effects of Cdc42 GTPase-activating protein Rga4. The respective levels of Gef1 and Rga4 proteins at the membrane define dynamically the growing area at each cell tip. Our findings show how the 14-3-3 protein Rad24 modulates the availability of Cdc42 GEF Gef1, a homologue of mammalian Cdc42 GEF DNMBP/TUBA, to spatially control Cdc42 GTPase activity and promote cell polarization and cell shape emergence.Work in F.V.’s laboratory is supported by National Institutes of Health R01 Grant GM095867. Part of this work was also supported by National Science Foundation Grant 0745129. J.R.Y. is supported by National Institutes of Health Grants P41 GM103533 and R01 MH 067880

Spatial control of translation repression and polarized growth by conserved NDR kinase Orb6 and RNA-binding protein Sts5

© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in eLife 5 (2016): e14216, doi:10.7554/eLife.14216.RNA-binding proteins contribute to the formation of ribonucleoprotein (RNP) granules by phase transition, but regulatory mechanisms are not fully understood. Conserved fission yeast NDR (Nuclear Dbf2-Related) kinase Orb6 governs cell morphogenesis in part by spatially controlling Cdc42 GTPase. Here we describe a novel, independent function for Orb6 kinase in negatively regulating the recruitment of RNA-binding protein Sts5 into RNPs to promote polarized cell growth. We find that Orb6 kinase inhibits Sts5 recruitment into granules, its association with processing (P) bodies, and degradation of Sts5-bound mRNAs by promoting Sts5 interaction with 14-3-3 protein Rad24. Many Sts5-bound mRNAs encode essential factors for polarized cell growth, and Orb6 kinase spatially and temporally controls the extent of Sts5 granule formation. Disruption of this control system affects cell morphology and alters the pattern of polarized cell growth, revealing a role for Orb6 kinase in the spatial control of translational repression that enables normal cell morphogenesis.Work in FV’s laboratory is supported by the National Institutes of Health R01 grant number GM095867. Part of this work was also supported by NSF grant 0745129. TT was supported by Japan Society for the Promotion of Science grants 16H02503 and 16K14672 and by Cancer Research UK

Epidemiological and clinical variables’ behavior in patients with stroke of Villa Clara

Background: cerebrovascular disease represents the most common health problem related to neurological care, it is important to study it in different contexts and from different approaches.Objective: to describe epidemiological and clinical variables’ behavior in patients admitted for stroke.Methods: descriptive and cross-sectional study, carried out in Arnaldo Milián Castro Hospital’s Neurology service from Villa Clara, Cuba, which included all patients with a clinical diagnosis of cardioembolic or atherothrombotic stroke, admitted to the ward during 2019. The information was obtained from the medical records stored in the Hospital Archive; and it was processed in the statistical package SPSS. v. 21. A descriptive statistical analysis was applied, in a frequency distribution.Results: female patients predominated (51.6%). There was a higher incidence in men older than 79 years (47.7%), and in women older than 70 (86.0%). In 67.3% the cardioembolic cause was demonstrated. Arterial hypertension was the main associated risk factor (83.6%). The motor defect was observed as the most frequent clinical finding on admission (96.7%). Hemorrhagic transformation of the infarct and nosocomial bronchopneumonia were identified as the main neurological and non-neurological complications, respectively. Patients discharged alive prevailed (68.6%).Conclusions: ischemic strokes are more frequent in elderly patients; early identification and timely management of the established disease can largely prevent the appearance of complications, and consequently death.</p

Two adaptation mechanisms regulate cellular migration in Dictyostelium discoideum

Dictyostelium discoideum is a simple model widely used to study many cellular functions, including differentiation, gene regulation, cellular trafficking and directional migration. Adaptation mechanisms are essential in the regulation of these cellular processes. The misregulation of adaptation components often results in persistent activation of signaling pathways and aberrant cellular responses. Studying adaptation mechanisms regulating cellular migration will be crucial in the treatment of many pathological conditions in which motility plays a central role, such as tumor metastasis and acute inflammation. I will describe two adaptation mechanisms regulating directional migration in Dictyostelium cells. The Extracellular signal Regulated Kinase 2 (ERK2) plays an essential role in Dictyostelium cellular migration. ERK2 stimulates intracellular cAMP accumulation in chemotaxing cells. Aberrant ERK2 regulation results in aberrant cAMP levels and defective directional migration. The MAP Phosphatase with Leucine-rich repeats (MPL1) is crucial for ERK2 adaptation. Cells lacking, MPL1 (mpl1- cells) displayed higher pre-stimulus and persistent post-stimulus ERK2 phosphorylation, defective cAMP production and reduced cellular migration. Reintroduction of a full length Mpl1 into mpl1- cells restored aggregation, ERK2 regulation, random and directional motility, and cAMP production similar to wild type cells (Wt). These results suggest Mpl1 is essential for proper regulation of ERK2 phosphorylation and optimal motility in Dictyostelium cells. Cellular polarization in Dictyostelium cells in part is regulated by the activation of the AGC-related kinase Protein Kinase Related B1 (PKBR1). The PP2A regulatory subunit, B56, and the Glycogen Synthase Kinase 3 (GSK3) are necessary for PKBR1 adaptation in Dictyostelium cells. Cells lacking B56, psrA-cells, exhibited high basal and post-stimulus persistent phosphorylation of PKBR1, increased phosphorylation of PKBR1 substrates, and aberrant motility. PKBR1 adaptation is also regulated by the GSK3. When the levels of active GSK3 are reduced in Wt and psrA- cells, high basal levels of phosphorylated PKBR1 were observed, in a Ras dependent, but B56 independent mechanism. Altogether, PKBR1 adaptation is regulated by at least two independent mechanisms: one by GSK3 and another by PP2A/B56

Conserved NDR/LATS kinase controls RAS GTPase activity to regulate cell growth and chronological lifespan

Adaptation to the nutritional environment is critical for all cells. RAS GTPase is a highly conserved GTP-binding protein with crucial functions for cell growth and differentiation in response to environmental conditions. Here, we describe a novel mechanism connecting RAS GTPase to nutrient availability in fission yeast. We report that the conserved NDR/LATS kinase Orb6 responds to nutritional cues and regulates Ras1 GTPase activity. Orb6 increases the protein levels of an Ras1 GTPase activator, the guanine nucleotide exchange factor Efc25, by phosphorylating Sts5, a protein bound to efc25 mRNA. By manipulating the extent of Orb6-mediated Sts5 assembly into RNP granules, we can modulate Efc25 protein levels, Ras1 GTPase activity, and, as a result, cell growth and cell survival. Thus, we conclude that the Orb6–Sts5–Ras1 regulatory axis plays a crucial role in promoting cell adaptation, balancing the opposing demands of promoting cell growth and extending chronological lifespan.</jats:p

Relación entre arquitectura del sueño y pronóstico global en pacientes con infarto cerebral total de circulación anterior

Ischemic strokes make up a group of disorders of the cerebral vasculature resulting from the occlusion of an extra vessel in the brain. Defining the prognosis of these patients during the acute phase is a complex estimation exercise, since various and interrelated factors are involved. The objective of this work is to estimate the possible relationship between Sleep Architecture and the clinical, vital and functional prognosis of patients with Total Cerebral Infarction of the Anterior Circulation (ITCA) during the acute phase. An analytical, longitudinal study was carried out in 35 adult patients with ITCA, from March 2017 to March 2018. The global prognosis and its categories were evaluated using the NIHSS scales, Barthel Index and modified Rankin. From inferential statistics, the independence test based on the Chi-square distribution and the Student's t-test were applied. Logistic regression was used to determine whether REM sleep duration behaved as an independent prognostic predictor. The results showed that the decrease in the time spent in the REM phase was very significantly related to a higher risk of death (t=-7.28; p=0.000); its duration was negatively correlated with the degree of neurological deficit (r=-0.529; p=0.001), and with the level of disability measured by the mRS 3 months after the stroke (r=-0.903; p=0.000), demonstrating in addition, a very significant and direct relationship with the BI scores (r=0.868; p=0.000). The decrease of one unit in the duration of REM sleep multiplies by 2.29 the possibility of an unfavorable result in these patients. It was concluded that the alterations of the Sleep Architecture, especially those that imply a decrease in the REM phase, have a negative impact on the evolution of patients with ITCA in the short and long term.Los accidentes cerebrovasculares isquémicos conforman un grupo de afecciones de la vasculatura cerebral resultante de la oclusión de un vaso suplementario del encéfalo. Definir el pronóstico de estos pacientes durante la fase aguda, es un complejo ejercicio de estimación, pues intervienen diversos e interrelacionados factores. El objetivo del presente trabajo consiste en estimar la posible relación entre la Arquitectura del Sueño y el pronóstico clínico, vital y funcional de pacientes con Infarto Cerebral Total de la Circulación Anterior (ITCA) durante la fase aguda. Se realizó un estudio analítico, longitudinal, en 35 pacientes adultos con ITCA, desde marzo 2017–marzo 2018. El pronóstico global y sus categorías se evaluaron utilizando las escalas de NIHSS, Índice de Barthel y Rankin modificada. De la estadística inferencial se aplicaron el test de independencia basado en la distribución Chi-cuadrado y la prueba t de Student. Se utilizó la regresión logística para determinar si la duración de la fase REM del sueño se comportaba como un predictor pronóstico independiente. Los resultados arrojaron que la disminución del tiempo transcurrido en la fase REM, se relacionó muy significativamente con mayor riesgo de muerte (t=-7.28; p=0.000); su duración se correlacionó negativamente con el grado de déficit neurológico (r=-0.529; p=0.001), y con el nivel de incapacidad medido por la mRS a los 3 meses del Ictus (r=-0.903; p=0.000), demostrándose además una relación muy significativa y directa con las puntuaciones del IB (r=0.868; p=0.000). La disminución de una unidad en la duración del sueño REM, multiplica en 2.29 la posibilidad del resultado no favorable en estos pacientes. Se concluyó que las alteraciones de la Arquitectura del Sueño, especialmente las que implican disminución de la fase REM, impactan negativamente en la evolución de pacientes con ITCA a corto y a largo plazo