👤 Eduardo Paz

Mitogen-activated protein kinase (MAPK) phosphatases [MKPs, also known as dual-specificity phosphatases (DUSPs)] regulate MAPKs -key mediators of cellular processes such as proliferation, differentiation, and survival- by dephosphorylating the threonine and tyrosine residues required for MAPK activation. MKP-3/DUSP6 is an ERK-selective phosphatase that has also been reported to regulate the transcription factor FOXO1. The full-length MKP-3 transcript has been shown to encode the MKP-3L protein, whereas alternative splicing gives rise to the shorter isoform MKP-3S. However, the available information regarding the functional differences between these variants is limited. By combining biochemical and bioinformatic approaches, we demonstrate that these isoforms differ significantly in subcellular localization and enzymatic activity. Structural analysis and molecular docking reveal that while MKP-3S retains functional binding domains and recognizes ERK2 similarly to the full-length isoform. However, the absence of critical catalytic motifs in MKP-3S leads to a structural uncoupling where the protein retains its ability to bind ERK2 but fails to induce dephosphorylation, suggesting a non-canonical role as a molecular scaffold. The results obtained demonstrate significant variations in subcellular localization, enzymatic activity, and the capacity to modulate FOXO1 transcriptional activity. This, in turn, affects the expression of genes such as p21. In conclusion, the findings indicate that MKP-3 variants exhibit distinct functional behaviours, which may result in differential regulation of a wide range of cellular processes. Show less

Tick infestation is one of the main challenges in tropical beef cattle production, leading to significant economic losses. Knowledge of the molecular factors underlying natural tick resistance in cattle contributes to genetic selection through the identification of biomarkers that can be used to accurately identify animals resistant to ticks. Although several genes associated with resistance to ticks have been identified, the molecular mechanisms underlying tick resistance are yet to be elucidated. This study investigated the biological processes, pathways, and key proteins involved in the resistance to the tick Rhipicephalus (Boophilus) microplus in a tropically adapted beef cattle breed. Tick resistance was evaluated in 162 Caracu cows. Blood samples were collected from a subset of 16 extreme animals, including eight with a high tick load (SUS) and eight with a low tick load (RES), for proteomic analysis by LC-MS/MS. A total of 172 and 34 proteins were exclusively identified in plasma samples from the SUS and RES groups, respectively. In addition, 14,034 proteins were detected in the blood plasma of both groups, of which 51 and 101 proteins were significantly increased in plasma samples of the SUS and RES groups, respectively. Among the top 20 proteins with the highest absolute log-fold change values, those encoded by the RNASE1, TNS2, NOXO1, ZNRF3, APOA4, KMT2B, RPS6KA5, PON1, C4BPA, SETD2, HP, TMEM63A, MAST2, and SETD1B genes were highlighted based on their functions that may contribute to a response to tick infestation. Functional enrichment analysis revealed 36 biological processes, 35 molecular functions, and 16 pathways to be significant (P < 0.05), highlighting those related to hemostasis, vesicular transport, cell proliferation and migration, calcium, actin, lipids, scavenger receptors, hydrogen peroxide, tyrosine, and insulin-like growth factor, which may contribute to tick resistance. In addition, PPI network analysis revealed several proteins involved in complement and coagulation systems, hematopoiesis, and immune response as important nodes, based on their centrality and edges. The identification of differentially abundant proteins between RES and SUS animals, as well as their relationships and roles in key biological processes and molecular pathways detected, contribute to improving our understanding of the mechanisms underlying tick resistance in naturally adapted cattle breeds. Furthermore, the differentially abundant proteins detected in this study are potential biomarkers for the response to R. microplus infestation. Show less

Heat stress has deleterious effects on physiological and performance traits in livestock. Within this context, using tropically adapted cattle breeds in pure herds or terminal crossbreeding schemes to explore heterosis is attractive for increasing animal production in warmer climate regions. This study aimed to identify biological processes, pathways, and potential biomarkers related to thermotolerance in Caracu, a tropically adapted beef cattle breed, by proteomic analysis of blood plasma. To achieve this goal, 61 bulls had their thermotolerance evaluated through a heat tolerance index. A subset of 14 extreme animals, including the seven most thermotolerant (HIGH group) and the seven least thermotolerant (LOW group), had their blood plasma samples used for proteomic analysis by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The differentially regulated proteins detected between HIGH and LOW groups were used to perform functional enrichment analysis and a protein-protein interaction network analysis. A total of 217 proteins were detected only in the HIGH thermotolerant group and 51 only in the LOW thermotolerant group. In addition, 81 and 87 proteins had significantly higher and lower abundancies in the HIGH group, respectively. Regarding proteins with the highest absolute log-fold change values, we highlighted those encoded by DUSP5, IGFALS, ROCK2, RTN4, IRAG1, and NNT genes based on their functions. The functional enrichment analysis detected several biological processes, molecular functions, and pathways related to cellular responses to stress, immune system, complement system, and hemostasis in both HIGH and LOW groups, in addition to terms and pathways related to lipids and calcium only in the HIGH group. Protein-protein interaction (PPI) network revealed as important nodes many proteins with roles in response to stress, hemostasis, immune system, inflammation, and homeostasis. Additionally, proteins with high absolute log-fold change values and proteins detected as essential nodes by PPI analysis highlighted herein are potential biomarkers for thermotolerance, such as ADRA1A, APOA1, APOB, APOC3, C4BPA, CAT, CFB, CFH, CLU, CXADR, DNAJB1, DNAJC13, DUSP5, FGA, FGB, FGG, HBA, HBB, HP, HSPD1, IGFALS, IRAG1, KNG1, NNT, OSGIN1, PROC, PROS1, ROCK2, RTN4, RYR1, TGFB2, VLDLR, VTN, and VWF. Identifying potential biomarkers, molecular mechanisms and pathways that act in response to heat stress in tropically adapted beef cattle contributes to developing strategies to improve performance and welfare traits in livestock under tropical climates. Show less

Type 2 diabetes mellitus leads to debilitating complications that affect the quality of life of many Filipinos. Genetic variability contributes to 30% to 70% of T2DM risk. Determining genomic variants related to type 2 diabetes mellitus susceptibility can lead to early detection to prevent complications. However, interethnic variability in risk and genetic susceptibility exists. This study aimed to identify variants associated with type 2 diabetes mellitus among Filipinos using a case-control design frequency matched for age and sex. A comparison was made between 66 unrelated Filipino adults with type 2 diabetes mellitus and 121 without. Genotyping was done using a candidate gene approach on genetic variants of type 2 diabetes mellitus and its complications involving allelic association and genotypic association studies with correction for multiple testing. Nine (9) significant variants, mostly involved in glucose and energy metabolism, associated with type 2 diabetes mellitus in Filipinos were found. Notably, a CDKAL1 variant (rs7766070) confers the highest level of risk while rs7119 (HMG20A) and rs708272 (CETP) have high risk allele frequencies in this population at 0.77 and 0.66, respectively, making them potentially good markers for type 2 diabetes mellitus screening. The data generated can be valuable in developing genetic risk prediction models for type 2 diabetes mellitus to diagnose and prevent the condition among Filipinos. Show less

MAPK phosphatases (MKP) downregulate the activity of mitogen-activated protein kinases (MAPK), such as ERK1/2, and modulate the processes regulated by these kinases. ERK1/2 participate in a wide range of processes including tissue-specific hormone-stimulated steroidogenesis. H295R cells are a suitable model for the study of human adrenal cortex functions, particularly steroid synthesis, and respond to angiotensin II (Ang II) triggering ERK1/2 phosphorylation in a transient fashion. MKP-3 dephosphorylates ERK1/2 and, as recently reported, forkhead box protein 1 (FOXO1). Here, we analyzed MKP-3 expression in H295R cells and its putative regulation by Ang II. Results showed the expression of MKP-3 full length (L) and a short splice variant (S), and the upregulation of both isoforms by Ang II. L and S messenger and protein levels increased 30 min after Ang II stimulation and declined over the next 3 h, a temporal frame compatible with ERK1/2 dephosphorylation. In addition, FOXO1 activation is known to include its dephosphorylation and nuclear translocation. Therefore, we analyzed the effect of Ang II on FOXO1 modulation. Ang II induced FOXO1 transient phosphorylation and translocation and also the induction of p21, a FOXO1-dependent gene, whereas MKP-3 knock-down reduced both FOXO1 translocation and p21 induction. These data suggest that, through MKP-3, Ang II counteracts its own effects on ERK1/2 activity and also triggers the activation of FOXO-1 and the induction of cell cycle inhibitor p21. Taken together, the current findings reveal the participation of MKP-3 not only in turn-off but also in turn-on signals which control important cellular processes. Show less

GIP action in type 2 diabetic (T2D) patients is altered. We hypothesized that methylation changes could be present in GIP receptor of T2D patients. This study aimed to assess the differences in DNA methylation profile of GIPR promoter between T2D patients and age- and Body Mass Index (BMI)-matched controls. We included 93 T2D patients (cases) that were uniquely on diet (without any anti-diabetic pharmacological treatment). We matched one control (with oral glucose tolerance test negative, non diabetic), by age and BMI, for every case. Cytokines and hormones were determined by ELISA. DNA was extracted from whole blood and DNA methylation was assessed using the Sequenom EpiTYPER system. Our results showed that T2D patients were more insulin resistant and had a poorer β cell function than their controls. Fasting adiponectin was lower in T2D patients as compared to controls (7.0±3.8 µgr/mL vs. 10.0±4.2 µgr/mL). Levels of IL 12 in serum were almost double in T2D patients (52.8±58.3 pg/mL vs. 29.7±37.4 pg/mL). We found that GIPR promoter was hypomethylated in T2D patients as compared to controls. In addition, HOMA-IR and fasting glucose correlated negatively with mean methylation of GIPR promoter, especially in T2D patients. This case-control study confirms that newly diagnosed, drug-naïve T2D patients are more insulin resistant and have worse β cell function than age- and BMI-matched controls, which is partly related to changes in the insulin-sensitizing metabolites (adiponectin), in the proinflammatory profile (IL12) and we suggest in the methylation pattern of GIPR. Our study provides novel findings on GIPR promoter methylation profile which may improve our ability to understand type 2 diabetes pathogenesis. Show less

A balanced translocation affecting DISC1 cosegregates with several psychiatric disorders, including schizophrenia, in a Scottish family. DISC1 is a hub protein of a network of protein-protein interactions involved in multiple developmental pathways within the brain. Gene set-based analysis has been proposed as an alternative to individual analysis of single nucleotide polymorphisms (SNPs) to get information from genome-wide association studies. In this work, we tested for an overrepresentation of the DISC1 interacting proteins within the top results of our ranked list of genes based on our previous genome-wide association study of missense SNPs in schizophrenia. Our data set consisted of 5100 common missense SNPs genotyped in 476 schizophrenic patients and 447 control subjects from Galicia, NW Spain. We used a modification of the Gene Set Enrichment Analysis adapted for SNPs, as implemented in the GenGen software. The analysis detected an overrepresentation of the DISC1 interacting proteins (permuted P-value=0.0158), indicative of the role of this gene set in schizophrenia risk. We identified seven leading-edge genes, MACF1, UTRN, DST, DISC1, KIF3A, SYNE1, and AKAP9, responsible for the overrepresentation. These genes are involved in neuronal cytoskeleton organization and intracellular transport through the microtubule cytoskeleton, suggesting that these processes may be impaired in schizophrenia. Show less

β-Secretase (β-site amyloid precursor protein-cleaving enzyme 1; BACE1) is a transmembrane aspartic protease that cleaves the β-amyloid precursor protein en route to generation of the amyloid β-peptide (Aβ) that is believed to be responsible for the Alzheimer's disease amyloid cascade. It is thus a prime target for the development of inhibitors which may serve as drugs in the treatment and/or prevention of Alzheimer's disease. In the following determination of the crystal structures of both apo and complexed BACE1, structural analysis of all crystal structures of BACE1 deposited in the PDB and molecular dynamics (MD) simulations of monomeric and `dimeric' BACE1 were used to study conformational changes in the active-site region of the enzyme. It was observed that a flap able to cover the active site is the most flexible region, adopting multiple conformational states in the various crystal structures. Both the presence or absence of an inhibitor within the active site and the crystal packing are shown to influence the flap's conformation. An open conformation of the flap is mostly observed in the apo structures, while direct hydrogen-bonding interaction between main-chain atoms of the flap and the inhibitor is a prerequisite for the flap to adopt a closed conformation in the crystal structures of complexes. Thus, a systematic study of the conformational flexibility of the enzyme may not only contribute to structure-based drug design of BACE1 inhibitors and of other targets with flexible conformations, but may also help to better understand the mechanistic events associated with the binding of substrates and inhibitors to the enzyme. Show less

Apolipoprotein IV (apo A-IV) has been related to fat absorption and to the activation of some of the enzymes involved in lipid metabolism. Several polymorphic sites within the gene locus for apo A-IV have been detected. Previous studies have shown that the A-IV-2 isoform produces a different plasma lipid response after the consumption of diets with different fat and cholesterol content. The present study was designed to evaluate whether the apo A-IV 360His polymorphism could explain, at least in part, the interindividual variability observed during postprandial lipemia. Fifty-one healthy male volunteers (42 homozygous for the apo A-IV 360Gln allele (Gln/Gln) and nine carriers of the A-IV-360His allele), homozygous for the apo E3 allele, were subjected to a vitamin A-fat load test consisting of 1 g of fat/kg body weight and 60000 IU of vitamin A. Blood was drawn at time 0 and every hour for 11 h. Plasma cholesterol (C), triacylglycerol (TG), and C, TG, apo B-100, apo B-48, apo A-IV and retinyl palmitate (RP) were determined in lipoprotein fractions. Data of postprandial lipemia revealed that subjects with the apo A-IV 360His allele had significantly greater postprandial levels in small triacylglycerol rich lipoproteins (TRL)-C (P<0.02), small TRL-TG (P<0.01) and large TRL-TG (P<0.05) than apo A-IV 360Gln/Gln subjects. In conclusion, the modifications observed in postprandial lipoprotein metabolism in subjects with the A-IV 360His allele could be involved in the different low density lipoprotein (LDL)-C responses observed in these subjects following a diet rich in cholesterol and saturated fats. Show less

We investigated the molecular basis for factor VII (FVII) deficiency in Israel and found that 13 patients were homozygous and 10 heterozygous for a C to T substitution at nucleotide 10648 of the FVII gene. This predicted an Ala244Val change and was associated with decreased FVII activity and antigen level. Of the 36 Ala244Val positive alleles, 20 were observed in patients of Moroccan origin, 10 in Iranian-Jewish patients and 6 in patients of other origins. A computer model of the serine protease domain of FVII suggested that the Ala244Val substitution may cause distortion of the entire protein structure. Intragenic polymorphic sites analyses disclosed a founder effect for the Moroccan and Iranian-Jewish patients. A survey of the Ala244Val mutation revealed an allele frequency of 1:42.5 in Moroccan Jews and 1:40 in Iranian Jews. As Moroccan Jews have been separated from Iranian Jews for more than two millennia, the data suggest that the Ala244Val mutation occurred in ancient times. Show less