Exon skipping truncates the PDZ domain of human erythroid p55 in a patient with chronic myeloid leukemia in acute megakaryoblastic blast crisis

Human p55, the major palmitoylated protein associated with the cytoplasmic face of the erythrocyte membrane, is believed to modulate interactions between protein 4.1 and glycophorin C. It is the prototype of a newly described family of signaling molecules that includes hD1g, the human homologue of the Drosophila discs-large tumor suppressor protein. Chronic myeloid leukemia is characterized by transformation to a fulminating acute leukemia, heralded by evolution of the Philadelphia chromosome positive genotype (Ph +) to further abnormalities. RT-PCR of p55 mRNA from a patient with acute megakaryoblastic CML revealed a 69 base pair deletion in the PDZ domain, corresponding to exon 5 of the p55 gene. The deletion of constitutive exon 5 not only marks the first abnormality of the p55 cDNA in human disease but also the first abnormality of a PDZ domain in human disease and may represent another genetic abnormality associated with CML in blast crisis.     

Phosphorylation-independent dual-site binding of the FHA domain of KIF13 mediates phosphoinositide transport via centaurin alpha1

Phosphatidylinositol 3,4,5-triphosphate (PIP3) plays a key role in neuronal polarization and axon formation. PIP3-containing vesicles are transported to axon tips by the kinesin KIF13B via an adaptor protein, centaurin α1 (CENTA1). KIF13B interacts with CENTA1 through its forkhead-associated (FHA) domain. We solved the crystal structures of CENTA1 in ligand-free, KIF13B-FHA domain-bound, and PIP3 head group (IP4)-bound conformations, and the CENTA1/KIF13B-FHA/IP4 ternary complex. The first pleckstrin homology (PH) domain of CENTA1 specifically binds to PIP3, while the second binds to both PIP3 and phosphatidylinositol 3,4-biphosphate (PI(3,4)P(2)). The FHA domain of KIF13B interacts with the PH1 domain of one CENTA1 molecule and the ArfGAP domain of a second CENTA1 molecule in a threonine phosphorylation-independent fashion. We propose that full-length KIF13B and CENTA1 form heterotetramers that can bind four phosphoinositide molecules in the vesicle and transport it along the microtubule.     

Unintentional injury mortality in the European Union: how many more lives could be saved?

AIMS: The wide variation of unintentional (accidental) injury mortality rates in the European Union (EU) member states suggests that there is high potential for prevention. This paper attempts to quantify the potential for saving lives in this part of the world if all 25 member states were to learn from the experience of countries with advanced injury prevention records. METHODS: Unintentional injury mortality data (latest three available years), including denominator population estimates, were obtained from the World Health Organization (WHO) mortality database for all 22 EU countries with a population of more than one million. Annual average age-adjusted injury mortality rates were used to derive the potential for saving of lives under two scenarios: (a) if all EU member states matched the country with the lowest unintentional rate for all causes of injury combined; (b) if the benchmark was alternatively the country with the lowest unintentional injury cause-specific rate. Separate calculations were performed for children (0-14), adults (15-64), and the elderly (65 and over). RESULTS: Under the first scenario, over 73,000 lives could have been saved in the EU 25 in a single year, notably nearly half (47.4%) fewer unintentional injury deaths could be observed in children, over half in adult (54%), and two-fifths (38%) in the elderly. Under the second, more optimistic, scenario 59% of childhood and adult and 75% of unintentional injury deaths among the elderly would have been avoided. CONCLUSIONS: A substantial proportion of lives lost due to unintentional injury might be saved if all countries were to achieve the lowest unintentional injury mortality rates in the EU. The above calculations are based on a simple theoretical model but there is increasing evidence on the array of existing effective preventive interventions and improved trauma care calls for public health action in each member state that could in practice halt, to the extent possible, the unintentional injury epidemic.     

Plasmodium falciparum cysteine protease falcipain-2 cleaves erythrocyte membrane skeletal proteins at late stages of parasite development

Plasmodium falciparum-derived cysteine protease falcipain-2 cleaves host erythrocyte hemoglobin at acidic pH and specific components of the membrane skeleton at neutral pH. Analysis of stage-specific expression of these 2 proteolytic activities of falcipain-2 shows that hemoglobin-hydrolyzing activity is maximum in early trophozoites and declines rapidly at late stages, whereas the membrane skeletal protein hydrolyzing activity is markedly increased at the late trophozoite and schizont stages. Among the erythrocyte membrane skeletal proteins, ankyrin and protein 4.1 are cleaved by native and recombinant falcipain-2 near their C-termini. To identify the precise peptide sequence at the hydrolysis site of protein 4.1, we used a recombinant construct of protein 4.1 as substrate followed by MALDI-MS analysis of the cleaved product. We show that falcipain-2-mediated cleavage of protein 4.1 occurs immediately after lysine 437, which lies within a region of the spectrin-actin-binding domain critical for erythrocyte membrane stability. A 16-mer peptide containing the cleavage site completely inhibited the enzyme activity and blocked falcipain-2-induced fragmentation of erythrocyte ghosts. Based on these results, we propose that falcipain-2 cleaves hemoglobin in the acidic food vacuole at the early trophozoite stage, whereas it cleaves specific components of the red cell skeleton at the late trophozoite and schizont stages. It is the proteolysis of skeletal proteins that causes membrane instability, which, in turn, facilitates parasite release in vivo.     

Parasites as Emerging Biomonitoring Tools-Promises and Pitfalls

Proceedings of the National Academy of Sciences, India Section B: Biological Sciences - The ongoing debate over the application of parasites as ecological indicators for environmental assessment is...     

Role of intraoperative cholangiography in detecting rare bile duct anomalies.

A case of an anomalous extrahepatic biliary system is reported in which the right hepatic duct was found to enter the infundibulum of the gallbladder. In this case, a selective intraoperative cholangiography has prevented a possible major iatrogenic injury.     

Effects of volume and surface property in hydrolysis by acetylcholinesterase. The trimethyl site

beta-Substituted ethyl acetates, XCH2CH2OCOCH3, have been prepared, and their hydrolysis by acetylcholinesterase has been studied. Log of enzymic reactivity, normalized for intrinsic reactivity in hydrolysis by hydroxide, log (kcat/Km)n, rises linearly with increasing refraction volume, MR (or RD25), for substrates with beta-X = H, Cl, Br, CH3CH2, (CH3)2CH, (CH3)2S+, (CH3)3N+, and (CH3)3C. Larger substituents may be accommodated, (CH3)3Si and (CH3CH2)3N+, with no further increase in rate. Substrates with beta-substituents CH3S, CH3S(O), (CH3)3N+(OH), and CH3S(O2) are less reactive than consistent with the relation with MR by factors of 5-40, indicating that hydrophobic surface and desolvation of the substrate--enzyme interface may be necessary for maximum reactivity correlated with MR. Values of log (kcat/Km)n for substrates with beta-substituents X = CH3S, Cl, Br, CH3CH2, (CH3)2CH, (CH3)3C, and (CH3)3Si rise linearly with increasing hydrophobicity, pi, but reactivity of substrates with X = (CH3)3N+ and (CH3)2S+ are more reactive than consistent with a relation to pi by factors of 300 and 40 and with X = CH3S(O2), CH3S(O), and (CH3)2N+(OH), by factors of 7-100. Reactivity appears related to (i) volume of the beta-substituent and its fit in its subsite, which is trimethyl rather than anionic, and (ii) the hydrophobicity of its surface.     

Novel peptidomimetic cysteine protease inhibitors as potential antimalarial agents

The synthesis of a new class of peptidomimetics 1a-j, based on a 1,4-benzodiazepine scaffold and on a C-terminal aspartyl aldehyde building block, is described. Compounds 1a-j provided significant inhibitory activity against falcipains 2A and 2B (FP-2A and FP-2B), two cysteine proteases from Plasmodium falciparum.