Polarized cell migration results from the transduction of extracellular cues promoting the activation of Rho GTPases with the intervention of multidomain proteins, including guanine exchange factors. P-Rex1 and P-Rex2 are Rac GEFs connecting G␤␥ and phosphatidylinositol 3-kinase signaling to Rac activation. Their complex architecture suggests their regulation by protein-protein interactions. Novel mechanisms of activation of Rho GTPases are associated with mammalian target of rapamycin (mTOR), a serine/ threonine kinase known as a central regulator of cell growth and proliferation. Recently, two independent multiprotein complexes containing mTOR have been described. mTORC1 links to the classical rapamycin-sensitive pathways relevant for protein synthesis; mTORC2 links to the activation of Rho GTPases and cytoskeletal events via undefined mechanisms. Here we demonstrate that P-Rex1 and P-Rex2 establish, through their tandem DEP domains, interactions with mTOR, suggesting their potential as effectors in the signaling of mTOR to Rac activation and cell migration. This possibility was consistent with the effect of dominant-negative constructs and short hairpin RNA-mediated knockdown of P-Rex1, which decreased mTOR-dependent leucine-induced activation of Rac and cell migration. Rapamycin, a widely used inhibitor of mTOR signaling, did not inhibit Rac activity and cell migration induced by leucine, indicating that P-Rex1, which we found associated to both mTOR complexes, is only active when in the mTORC2 complex. mTORC2 has been described as the catalytic complex that phosphorylates AKT/PKB at Ser-473 and elicits activation of Rho GTPases and cytoskeletal reorganization. Thus, P-Rex1 links mTOR signaling to Rac activation and cell migration.P-Rex1 and P-Rex2 are Rac guanine exchange factors connecting G protein-coupled receptors, through G␤␥ and phosphatidylinositol 3-kinase, to Rac activation. In particular, P-Rex1 has been associated with the activation of Rac2, generating reactive oxygen species in neutrophils. P-Rex2 (showing two splice variants) is similarly regulated by G␤␥ and phosphatidylinositol 3-kinase. Northern blot assays revealed a differential distribution of the two members of the P-Rex 3 family, suggesting that they exert equivalent functions in different cellular populations (1-3, 7-11). The complex architecture of this family of proteins, constituted by a catalytic DH domain, followed by a phosphatidylinositol 3,4,5-trisphosphate-sensitive pleckstrin homology domain, two DEP and two PDZ domains in tandem, and a long carboxyl terminus (except for P-Rex2b, which is the short version, having a reduced carboxyl terminus), suggests that these Rac guanine exchange factors might be regulated by diverse protein-protein interactions modulating signal transduction pathways associated with the activation of Rac. In fact, in the developing brain, P-Rex1 is associated with neuronal migration in response to nerve growth factor (12, 13).The mammalian target of rapamycin, mTOR, a highly conserved serine-threonine k...

It has been suggested that oxidative stress may participate in the progression of diabetes and its complications. Long-term complications of type 2 diabetes mellitus (T2DM) include retinopathy, atherosclerosis, shortened life span of erythrocytes, nephropathy, and chronic kidney disease (CKD). Oxidative damage has been associated with erythrocyte apoptosis induction in other pathological conditions. Our aim was to study the presence of eryptosis and its possible relationship with oxidative damage in patients with T2DM without CKD (T2DM/CKD(-)) and in patients with T2DM and CKD (T2DM/CKD(+)).Oxidative damage of lipids erythrocytes were increased in diabetic patients. The highest lipoperoxidation was found in T2DM/CKD(+). Likewise, the lower plasma total antioxidant capacity, GSH/GSSG ratio, and GSH in erythrocytes were found in T2DM/CKD(+) patients. A negative correlation was found between plasma total antioxidant capacity and oxidative damage. Phosphatidylserine (PS) externalization was measured in erythrocytes to evaluate eryptosis. Annexin binding in erythrocytes of T2DM/CKD(+) patients was higher than in healthy subjects and T2DM/CKD(-) patients. A positive correlation between lipoperoxidation and PS externalization in erythrocytes was found. This work showed that the erythrocytes of diabetic patients have increased oxidative damage, a reduction of antioxidant systems and more erythrocyte PS externalization. The duration of diabetes and the presence of CKD increase both oxidative damage and eryptosis. It is possible that a longer time of evolution induces an increase in erythrocyte oxidative damage and the consumption of blood antioxidant systems, adding to the osmotic stress in CKD and so contributes to an increase in PS externalization in diabetic patients.

The absence of ZO-2 promotes an increase in cell size by two mechanisms: an increase in cyclin D, which extends the time that the cells spend in the G1 phase of the cell cycle, and an accumulation of YAP at the nucleus, which promotes its transcriptional activity, triggering the activation of the mTORC1 complex and its target, S6K1.

Copper [Cu(II)] is an ubiquitous transition and trace element in living organisms. It increases reactive oxygen species (ROS) and free-radical generation that might damage biomolecules like DNA, proteins, and lipids. Furthermore, ability of Cu(II) greatly increases in the presence of oxidants. ROS, like hydroxyl (.OH) and superoxide (.O(2)) radicals, alter both the structure of the DNA double helix and the nitrogen bases, resulting in mutations like the AT-->GC and GC-->AT transitions. Proteins, on the other hand, suffer irreversible oxidations and loss in their biological role. Thus, the aim of this investigation is to characterize, in vitro, the structural effects caused by ROS and Cu(II) on bacteriophage lambda DNA or proteins using either hydrogen peroxide (H(2)O(2)) or ascorbic acid with or without Cu(II). Exposure of DNA to ROS-generating mixtures results in electrophoretic (DNA breaks), spectrophotometric (band broadening, hypochromic, hyperchromic, and bathochromic effects), and calorimetric (denaturation temperature [T(d)], denaturation enthalpy [DeltaH], and heat capacity [C(p)] values) changes. As for proteins, ROS increased their thermal stability. However, the extent of the observed changes in DNA and proteins were distinct, depending on the efficiency of the systems assayed to generate ROS. The resulting effects were most evident when Cu(II) was present. In summary, these results show that the ROS, .O2 and .OH radicals, generated by the Cu(II) systems assayed deeply altered the chemical structure of both DNA and proteins. The physiological relevance of these structural effects should be further investigated.

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