DOCK4 and CEACAM21 as novel schizophrenia candidate genes in the Jewish population.

It is well accepted that schizophrenia has a strong genetic component. Several genome-wide association studies (GWASs) of schizophrenia have been published in recent years ; most of them population based with a case-control design. Nevertheless, identifying the specific genetic variants which contribute to susceptibility to the disorder remains a challenging task. A family-based GWAS strategy may be helpful in the identification of schizophrenia susceptibility genes since it is protected against population stratifi- cation, enables better accounting for genotyping errors and is more sensitive for identification of rare variants which have a very low frequency in the general population. In this project we implemented a family-based GWAS of schizophrenia in a sample of 107 Jewish-Israeli families. We found one genome- wide significant association in the intron of the DOCK4 gene (rs2074127, p value=1.134r10 x 7 ) and six additional nominally significant association signals with p<1r10 x 5 . One of the top single nucleotide polymorphisms (p<1r10 x 5 ) which is located in the predicted intron of the CEACAM21 gene was significantly replicated in independent family-based sample of Arab-Israeli origin (rs4803480 : p value=0.002 ; combined p value=9.61r10x8), surviving correction for multiple testing. Both DOCK4 and CEACAM21 are biologically reasonable candidate genes for schizophrenia although generalizability of the association of DOCK4 with schizophrenia should be investigated in further studies. In addition, gene-wide significant associations were found within three schizophrenia candidate genes : PGBD1, RELN and PRODH, replicating previously reported associations. By application of a family-based strategy to GWAS, our study revealed new schizophrenia susceptibility loci in the Jewish-Israeli popu- lation. Received 8 March 2011 ; Reviewed 11 April 2011 ; Revised 19 April 2011 ; Accepted 13 May 201

Apicomplexan Parasites Co-Opt Host Calpains to Facilitate Their Escape from Infected Cells

Apicomplexan parasites, including Plasmodium falciparum and Toxoplasma gondii (the causative agents of malaria and toxoplasmosis, respectively), are responsible for considerable morbidity and mortality worldwide. These pathogenic protozoa replicate within an intracellular vacuole inside of infected host cells, from which they must escape to initiate a new lytic cycle. By integrating cell biological, pharmacological, and genetic approaches, we provide evidence that both Plasmodium and Toxoplasma hijack host cell calpain proteases to facilitate parasite egress. Immunodepletion or inhibition of calpain-1 in hypotonically lysed and resealed erythrocytes prevented the escape of P. falciparum parasites, which was restored by adding purified calpain-1. Similarly, efficient egress of T. gondii from mammalian fibroblasts was blocked by either small interfering RNA– mediated suppression or genetic deletion of calpain activity and could be restored by genetic complementation

Platelet Factor 4 Activity against P. falciparum and Its Translation to Nonpeptidic Mimics as Antimalarials

SummaryPlasmodium falciparum pathogenesis is affected by various cell types in the blood, including platelets, which can kill intraerythrocytic malaria parasites. Platelets could mediate these antimalarial effects through human defense peptides (HDPs), which exert antimicrobial effects by permeabilizing membranes. Therefore, we screened a panel of HDPs and determined that human platelet factor 4 (hPF4) kills malaria parasites inside erythrocytes by selectively lysing the parasite digestive vacuole (DV). PF4 rapidly accumulates only within infected erythrocytes and is required for parasite killing in infected erythrocyte-platelet cocultures. To exploit this antimalarial mechanism, we tested a library of small, nonpeptidic mimics of HDPs (smHDPs) and identified compounds that kill P. falciparum by rapidly lysing the parasite DV while sparing the erythrocyte plasma membrane. Lead smHDPs also reduced parasitemia in a murine malaria model. Thus, identifying host molecules that control parasite growth can further the development of related molecules with therapeutic potential

Association of the Type 2 Diabetes Mellitus Susceptibility Gene, TCF7L2, with Schizophrenia in an Arab-Israeli Family Sample

Many reports in different populations have demonstrated linkage of the 10q24–q26 region to schizophrenia, thus encouraging further analysis of this locus for detection of specific schizophrenia genes. Our group previously reported linkage of the 10q24–q26 region to schizophrenia in a unique, homogeneous sample of Arab-Israeli families with multiple schizophrenia-affected individuals, under a dominant model of inheritance. To further explore this candidate region and identify specific susceptibility variants within it, we performed re-analysis of the 10q24-26 genotype data, taken from our previous genome-wide association study (GWAS) (Alkelai et al, 2011). We analyzed 2089 SNPs in an extended sample of 57 Arab Israeli families (189 genotyped individuals), under the dominant model of inheritance, which best fits this locus according to previously performed MOD score analysis. We found significant association with schizophrenia of the TCF7L2 gene intronic SNP, rs12573128, (p = 7.01×10−6) and of the nearby intergenic SNP, rs1033772, (p = 6.59×10−6) which is positioned between TCF7L2 and HABP2. TCF7L2 is one of the best confirmed susceptibility genes for type 2 diabetes (T2D) among different ethnic groups, has a role in pancreatic beta cell function and may contribute to the comorbidity of schizophrenia and T2D. These preliminary results independently support previous findings regarding a possible role of TCF7L2 in susceptibility to schizophrenia, and strengthen the importance of integrating linkage analysis models of inheritance while performing association analyses in regions of interest. Further validation studies in additional populations are required

The Trypanosoma cruzi Protease Cruzain Mediates Immune Evasion

Trypanosoma cruzi is the causative agent of Chagas ’ disease. Novel chemotherapy with the drug K11777 targets the major cysteine protease cruzain and disrupts amastigote intracellular development. Nevertheless, the biological role of the protease in infection and pathogenesis remains unclear as cruzain gene knockout failed due to genetic redundancy. A role for the T. cruzi cysteine protease cruzain in immune evasion was elucidated in a comparative study of parental wild typeand cruzain-deficient parasites. Wild type T. cruzi did not activate host macrophages during early infection (,60 min) and no increase in,P ikBwas detected. The signaling factor NF-kB P65 colocalized with cruzain on the cell surface of intracellular wild type parasites, and was proteolytically cleaved. No significant IL-12 expression occurred in macrophages infected with wild type T. cruzi and treated with LPS and BFA, confirming impairment of macrophage activation pathways. In contrast, cruzain-deficient parasites induced macrophage activation, detectable ikB phosphorylation, and nuclear NF-kB P65 localization. These parasites were unable to develop intracellularly and survive within macrophages. IL 12 expression levels in macrophages infected with cruzain-deficient T. cruzi were comparable to LPS activated controls. Thus cruzain hinders macrophage activation during the early (,60 min) stages of infection, by interruption of the NF-kB P65 mediated signaling pathway. These early events allow T. cruzi survival and replication, and may lead to the spread of infection in acut

Thioamide-Based Fluorescent Protease Sensors

Thioamide quenchers can be paired with compact fluorophores to design “turn-on” fluorescent protease substrates. We have used this method to study a variety of serine-, cysteine-, carboxyl-, and metallo-proteases, including trypsin, chymotrypsin, pepsin, thermolysin, papain, and calpain. Since thioamides quench some fluorophores red-shifted from those naturally occurring in proteins, this technique can be used for real time monitoring of protease activity in crude preparations of virtually any protease. We demonstrate the value of this method in three model applications: (1) characterization of papain enzyme kinetics using rapid-mixing experiments, (2) selective monitoring of cleavage at a single site in a peptide with multiple proteolytic sites, and (3) analysis of the specificity of an inhibitor of calpain in cell lysates

The malaria parasite progressively dismantles the host erythrocyte cytoskeleton for efficient egress

10.1074/mcp.M111.010678Molecular and Cellular Proteomics1012-MCPO