The ER-embedded UBE2J1/RNF26 ubiquitylation complex exerts spatiotemporal control over the endolysosomal pathway

1. Download : Download high-res image (149KB)
2. Download : Download full-size image

     

Interaction between the inducible 70-kDa heat shock protein and autophagy: effects on fertility and pregnancy

A consequence of hsp70 (HSPA1A) induction is the inhibition of autophagy. Evidence of autophagy involvement in all aspects of the reproductive process is reviewed, and possible consequences of hsp70 induction at each developmental stage are postulated. It is proposed that aberrant external or internal stimuli that result in high levels of hsp70 production interfere with normal autophagy-related functions and lead to a decrease in the number of functional ova and spermatozoa, impaired pre- and post-implantation embryo development, and increased susceptibility to premature labor and delivery. The purpose of this review is to increase understanding of hsp70-autophagy interactions during reproduction. Interventions to modulate this interaction will lead to development of novel protocols to improve fertility and pregnancy outcome.     

Red blood cell rouleaux formation in dextran solution: dependence on polymer conformation

The velocity of rouleaux formation (RF), as previously shown, increases with increasing dextran concentration up to a critical concentration (C_a), beyond which the addition of dextran reduces the RF velocity (RFV). de Gennes' model for polymer solutions suggests that dextrans exist in two conformations: a coil structure at low concentrations, which changes to a network beyond a critical concentration (C^*). In the present study we examined the relation between C_a and C^* for dextrans of different molecular weight, and found that they coincide. This suggests that the change in dextran behavior, from increasing to decreasing RFV, occurs when their conformation changes from coil to network. In addition, it has been reported that in dilute dextran solutions the intercellular distance (D) between RBC in rouleaux increases with the molecular weight of the dextran. We found that D correlates with R_f, the end-to-end distance of the polymer molecule, and for all dextrans D ≤ 1.5 R_f. In accord with de Gennes' Model for polymers between surfaces, this corresponds to intercellular interaction with two overlapping surface-associated polymer layers, which may extend “tails” to interact with the opposing cells. Received: 8 August 1997 / Accepted: 28 November 1997     

Are ghost crabs (Ocypode spp.) smaller on human-disturbed sandy beaches? A global analysis

Hydrobiologia - Testing ghost crabs as indicator species usually fail to depict the mechanisms behind low burrow densities in urban coasts, neglecting individual traits as diagnostic variables. We...     

Adenylyl cyclase P-site ligands accelerate differentiation in Ob1771 preadipocytes

Differentiation of Ob1771 preadipocytes to adipocytes wascharacterized by morphological changes and elevated expression of thespecific marker enzyme, glycerol-3-phosphate dehydrogenase. Adifferentiation response substantially more complete and rapid thanthat obtained with insulin and 3,5,3'-triiodothyronine was observed with established inhibitors of adenylyl cyclases:2',5'-dideoxyadenosine (2',5'-dd-Ado),9-(cyclopentyl)adenine (9-CP-Ade), and 9-(arabinofuranosyl)adenine (9-Ara-Ade), coincident with decreased cellular cAMP levels. These ligands inhibit adenylyl cyclases noncompetitively, via a domain referred to as the P-site because of its requirement for an intact purine moiety. Differentiation was not induced by inosine, a nucleoside known not to act at the P-site, or byN⁶-(2-phenylisopropyl)adenosineor 1,3-diethyl-8-phenylxanthine, agonist and antagonist, respectively,for adenosine A₁ receptors. Alsoineffective were IBMX or forskolin, agents that can raise intracellularcAMP levels. Potency of the differentiation response followed the order2',5'-dd-Ado (1-20 µM) > 9-CP-Ade (10-100µM) = 9-Ara-Ade (10-100 µM) >> inosine, consistent withtheir potencies to inhibit adenylyl cyclases. The data suggest thatinhibition of adenylyl cyclase via the P-site and the consequentreduction in cell cAMP levels facilitate the induction ofdifferentiation in Ob1771 cells. The findings raise the questionwhether the known endogenous P-site ligands participate in thedifferentiation response induced by hormones.     

Diagnosis of Cell Death by Means of Infrared Spectroscopy

Fourier transform infrared (FTIR) spectroscopy has been established as a fast spectroscopic method for biochemical analysis of cells and tissues. In this research we aimed to investigate FTIR's utility for identifying and characterizing different modes of cell death, using leukemic cell lines as a model system. CCRF-CEM and U937 leukemia cells were treated with arabinoside and doxorubicin apoptosis inducers, as well as with potassium cyanide, saponin, freezing-thawing, and H₂O₂ necrosis inducers. Cell death mode was determined by various gold standard biochemical methods in parallel with FTIR-microscope measurements. Both cell death modes exhibit large spectral changes in lipid absorbance during apoptosis and necrosis; however, these changes are similar and thus cannot be used to distinguish apoptosis from necrosis. In contrast to the above confounding factor, our results reveal that apoptosis and necrosis can still be distinguished by the degree of DNA opaqueness to infrared light. Moreover, these two cell death modes also can be differentiated by their infrared absorbance, which relates to the secondary structure of total cellular protein. In light of these findings, we conclude that, because of its capacity to monitor multiple biomolecular parameters, FTIR spectroscopy enables unambiguous and easy analysis of cell death modes and may be useful for biochemical and medical applications.     

A multifaceted cellular damage repair and prevention pathway promotes high‐level tolerance to β‐lactam antibiotics

Bactericidal antibiotics are powerful agents due to their ability to convert essential bacterial functions into lethal processes. However, many important bacterial pathogens are remarkably tolerant against bactericidal antibiotics due to inducible damage repair responses. The cell wall damage response two‐component system VxrAB of the gastrointestinal pathogen Vibrio cholerae promotes high‐level β‐lactam tolerance and controls a gene network encoding highly diverse functions, including negative control over multiple iron uptake systems. How this system contributes to tolerance is poorly understood. Here, we show that β‐lactam antibiotics cause an increase in intracellular free iron levels and collateral oxidative damage, which is exacerbated in the ∆vxrAB mutant. Mutating major iron uptake systems dramatically increases ∆vxrAB tolerance to β‐lactams. We propose that VxrAB reduces antibiotic‐induced toxic iron and concomitant metabolic perturbations by downregulating iron uptake transporters and show that iron sequestration enhances tolerance against β‐lactam therapy in a mouse model of cholera infection. Our results suggest that a microorganism''s ability to counteract diverse antibiotic‐induced stresses promotes high‐level antibiotic tolerance and highlights the complex secondary responses elicited by antibiotics.     

Tyrosine Phosphorylation of Protein Kinase Cδ Is Essential for Its Apoptotic Effect in Response to Etoposide

Protein kinase Cdelta (PKCdelta) is involved in the apoptosis of various cells in response to diverse stimuli. In this study, we characterized the role of PKCdelta in the apoptosis of C6 glioma cells in response to etoposide. We found that etoposide induced apoptosis in the C6 cells within 24 to 48 h and arrested the cells in the G(1)/S phase of the cell cycle. Overexpression of PKCdelta increased the apoptotic effect induced by etoposide, whereas the PKCdelta selective inhibitor rottlerin and the PKCdelta dominant-negative mutant K376R reduced this effect compared to control cells. Etoposide-induced tyrosine phosphorylation of PKCdelta and its translocation to the nucleus within 3 h was followed by caspase-dependent cleavage of the enzyme. Using PKC chimeras, we found that both the regulatory and catalytic domains of PKCdelta were necessary for its apoptotic effect. The role of tyrosine phosphorylation of PKCdelta in the effects of etoposide was examined using cells overexpressing a PKCdelta mutant in which five tyrosine residues were mutated to phenylalanine (PKCdelta5). These cells exhibited decreased apoptosis in response to etoposide compared to cells overexpressing PKCdelta. Likewise, activation of caspase 3 and the cleavage of the PKCdelta5 mutant were significantly lower in cells overexpressing PKCdelta5. Using mutants of PKCdelta altered at individual tyrosine residues, we identified tyrosine 64 and tyrosine 187 as important phosphorylation sites in the apoptotic effect induced by etoposide. Our results suggest a role of PKCdelta in the apoptosis induced by etoposide and implicate tyrosine phosphorylation of PKCdelta as an important regulator of this effect.