Molecular interactions of ASPP1 and ASPP2 with the p53 protein family and the apoptotic promoters PUMA and Bax

The apoptosis stimulating p53 proteins, ASPP1 and ASPP2, are the first two common activators of the p53 protein family that selectively enable the latter to regulate specific apoptotic target genes, which facilitates yes yet unknown mechanisms for discrimination between cell cycle arrest and apoptosis. To better understand the interplay between ASPP- and p53-family of proteins we investigated the molecular interactions between them using biochemical methods and structure-based homology modelling. The data demonstrate that: (i) the binding of ASPP1 and ASPP2 to p53, p63 and p73 is direct; (ii) the C-termini of ASPP1 and ASPP2 interact with the DNA-binding domains of p53 protein family with dissociation constants, K_d, in the lower micro-molar range; (iii) the stoichiometry of binding is 1:1; (iv) the DNA-binding domains of p53 family members are sufficient for these protein–protein interactions; (v) EMSA titrations revealed that while tri-complex formation between ASPPs, p53 family of proteins and PUMA/Bax is mutually exclusive, ASPP2 (but not ASPP1) formed a complex with PUMA (but not Bax) and displaced p53 and p73. The structure-based homology modelling revealed subtle differences between ASPP2 and ASPP1 and together with the experimental data provide novel mechanistic insights.     

Assembly of mitochondrial cytochrome c-oxidase, a complicated and highly regulated cellular process

Cytochrome c-oxidase (COX), the terminal enzyme of the mitochondrial respiratory chain, plays a key role in the regulation of aerobic production of energy. Biogenesis of eukaryotic COX involves the coordinated action of two genomes. Three mitochondrial DNA-encoded subunits form the catalytic core of the enzyme, which contains metal prosthetic groups. Another 10 subunits encoded in the nuclear DNA act as a protective shield surrounding the core. COX biogenesis requires the assistance of >20 additional nuclear-encoded factors acting at all levels of the process. Expression of the mitochondrial-encoded subunits, expression and import of the nuclear-encoded subunits, insertion of the structural subunits into the mitochondrial inner membrane, addition of prosthetic groups, assembly of the holoenzyme, further maturation to form a dimer, and additional assembly into supercomplexes are all tightly regulated processes in a nuclear-mitochondrial-coordinated fashion. Such regulation ensures the building of a highly efficient machine able to catalyze the safe transfer of electrons from cytochrome c to molecular oxygen and ultimately facilitate the aerobic production of ATP. In this review, we will focus on describing and analyzing the present knowledge about the different regulatory checkpoints in COX assembly and the dynamic relationships between the different factors involved in the process. We have used information mostly obtained from the suitable yeast model, but also from bacterial and animal systems, by means of large-scale genetic, molecular biology, and physiological approaches and by integrating information concerning individual elements into a cellular system network.     

The substrate specificity of cruzipain 2, a cysteine protease isoform from Trypanosoma cruzi

Papain-like cysteine proteases are important for the survival of the flagellated protozoa Trypanosoma cruzi, the causative agent of Chagas' Disease. The lysosomal cysteine protease designated as cruzipain or cruzain, is the archetype of a multigene family of related isoforms. We investigated the substrate specificity of the cruzipain 2 isoform using internally quenched fluorogenic substrates. We found that cruzipain 2 and cruzain differ substantially regarding the specificity in the S2, S'1 and S'2 pockets. Our study indicates that cruzipain 2 has a more restricted specificity than cruzain, suggesting that these isoforms might act on distinct natural substrates.     

The primate-specific protein TBC1D3 is required for optimal macropinocytosis in a novel ARF6-dependent pathway

The generation of novel genes and proteins throughout evolution has been proposed to occur as a result of whole genome and gene duplications, exon shuffling, and retrotransposition events. The analysis of such genes might thus shed light into the functional complexity associated with highly evolved species. One such case is represented by TBC1D3, a primate-specific gene, harboring a TBC domain. Because TBC domains encode Rab-specific GAP activities, TBC-containing proteins are predicted to play a major role in endocytosis and intracellular traffic. Here, we show that the TBC1D3 gene originated late in evolution, likely through a duplication of the RNTRE locus, and underwent gene amplification during primate speciation. Despite possessing a TBC domain, TBC1D3 is apparently devoid of Rab-GAP activity. However, TBC1D3 regulates the optimal rate of epidermal growth factor–mediated macropinocytosis by participating in a novel pathway involving ARF6 and RAB5. In addition, TBC1D3 binds and colocalize to GGA3, an ARF6-effector, in an ARF6-dependent manner, and synergize with it in promoting macropinocytosis, suggesting that the two proteins act together in this process. Accordingly, GGA3 siRNA-mediated ablation impaired TBC1D3-induced macropinocytosis. We thus uncover a novel signaling pathway that appeared after primate speciation. Within this pathway, a TBC1D3:GGA3 complex contributes to optimal propagation of signals, ultimately facilitating the macropinocytic process.     

The cardiovascular profile of soccer referees: an echocardiographic study

Background

Previous studies demonstrated a modest association between C-Reactive Protein (CRP), stenosis of carotid artery, and carotid Intima-Media Thickness (IMT) in general population. During present study, we aimed to evaluate the relationship between High Sensitivity C-Reactive Protein (hsCRP) and Common Carotid Intima-Media Thickness (CCIMT) in patients who candidate for Coronary Artery Bypass Grafting (CABG).

Methods

The study subjects were enrolled from patients with coronary arteries disease referred from Shahid Madani Hospital (Tabriz, Iran), who have been candidate for elective CABG from January 2005 to August 2007. The common carotid arteries were evaluated with high-resolution B-mode ultrasonography using a 7.5- MHz linear-array transducer to determine the IMT and grade of stenosis. Serum hsCRP level was measured using commercially available enzyme linked immunosorbent assay kit.

Results

Finally, information of 176 CABG candidates was analysed. The mean age of participants was 62.71 ± 9.45 years with 1.63 male to female ratio. The mean of CCIMT was 0.69 ± 0.54 mm. Although there was no significant correlation between serum hsCRP level and CCIMT in patients without carotid stenosis (p=0.113, r=0.186), participants with common carotid artery stenosis had higher levels of serum hsCRP than participants without stenosis (2.42+/-1.30 vs. 1.20+/-0.97 mg/dl; p=0.009).

Conclusion

Study results showed that there was no correlation between serum hsCRP level and CCIMT in patients without carotid stenosis, but patients with common carotid artery stenosis had higher levels of serum hsCRP than patients without stenosis.     

High sensitivity C-reactive protein is associated with lower tibial cartilage volume but not lower patella cartilage volume in healthy women at mid-life

Introduction  

Elevated serum high sensitivity C-reactive protein (hsCRP) has been reported in established osteoarthritis (OA). The aim of this study was to determine whether serum levels of hsCRP are associated with the variation in tibial and patella cartilage volumes in women without evidence of OA.