Toll-like receptors (TLRs) and members of their signalling pathway play an important role in the initiation of the innate immune response to a wide variety of pathogens1,2,3. The adaptor protein TIRAP mediates downstream signalling of 5,6. We report a case-control genetic association study of 6106 individuals from Gambia, Kenya, United Kingdom, and Vietnam, with invasive pneumococcal disease, bacteraemia, malaria and tuberculosis. Thirty-three SNPs were genotyped, including TIRAP S180L. Heterozygous carriage of this variant was found to associate independently with all four infectious diseases in the different study populations (P=0.003, OR=0.59, 95%CI 0.42-0.83 for IPD; P=0.003, OR=0.40, 95%CI 0.21-0.77 for bacteraemia; P=0.002, OR=0.47, 95%CI 0.28-0.76 for malaria; P=0.008, OR=0.23 95%CI 0.07-0.73 for tuberculosis). Substantial support for a protective effect of S180L heterozygosity against infectious diseases was observed when the study groups were combined (N=6106, OverallCorrespondence should be addressed on genetics to AVSH (adrian.hill@well.ox.ac.uk) In the UK population, heterozygosity at TIRAP S180L was associated with protection from invasive pneumococcal disease (3×2 χ 2 =8.72, P=0.013, Table 1). An excess of mutant homozygotes amongst IPD cases (Table 1) was also observed in this UK population. TIRAP S180L was then examined in a separate group of UK individuals with thoracic empyema and a second control group. Although no association was observed between genotype and susceptibility to thoracic empyema overall (n=584, 3×2 χ 2 =0.63, P=0.73), analysis of the small subgroup of individuals with pneumococcal empyema revealed a non-significant trend towards association (3×2 χ 2 =5.05, P=0.080; Table 1). Interestingly, an excess of mutant homozygotes was again observed amongst this second group of IPD cases (Table 1).We then studied TIRAP S180L in a second population with invasive bacterial disease, comprising Kenyan children with well-defined bacteraemia. Although the mutant allele was found to be less common in the Kenyan population than in UK individuals, the same pattern of association was observed. The TIRAP S180L heterozygotes were significantly more common amongst community controls (5.9%), compared to individuals with bacteraemia (2.4%) (2×2 χ 2 =9.05, P=0.003; Table 1). The heterozygote protective effect of the S180L locus was also significant within the subgroup of 164 Kenyan children with pneumococcal bacteraemia (F exact =0.024, Table 1), thus replicating the findings in the UK studies.In the Gambian malaria case-control study, TIRAP S180L heterozygosity demonstrated a significant protective effect against both general malaria (Wald=8.35, P=0.004, Table 1) and severe malaria (Wald=8.706, P=0.003, Table 1). This result was replicated in a second malaria case-control study, this time in a Vietnamese population whose design included only cases of severe malaria: TIRAP S180L heterozygotes were again found to be more prevalent Finally, the possible effect of the TIRAP S180L polymorphism on ...

AMP-activated protein kinase (AMPK) is the downstream component of a protein kinase cascade that plays a key role in the regulation of energy metabolism. In humans, mutations in the gamma2-subunit of AMPK cause cardiac hypertrophy associated with Wolff-Parkinson-White syndrome, characterized by ventricular preexcitation. The effect of these mutations on AMPK activity and in development of the disease is enigmatic. Here we report that transgenic mice with cardiac-specific expression of gamma2 harboring a mutation of arginine residue 531 to glycine (RG-TG) develop a striking cardiac phenotype by 4 wk of age, including hypertrophy, impaired contractile function, electrical conduction abnormalities, and marked glycogen accumulation. At this stage, AMPK activity isolated from hearts of RG-TG mice was almost completely abolished but could be restored after phosphorylation by an upstream AMPK kinase. At 1 wk of age, there was no detectable evidence of a cardiac phenotype, and AMPK activity in RG-TG hearts was similar to that in nontransgenic, control mice. We propose that mutations in gamma2 lead to suppression of total cardiac AMPK activity secondary to increased glycogen accumulation. The subsequent decrease in AMPK activity provides a mechanism that may explain the development of cardiac hypertrophy in this model.

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The trimeric protein AMP-activated protein kinase (AMPK) is an important sensor of energetic status and cellular stress, and mutations in genes encoding two of the regulatory γ subunits cause inherited disorders of either cardiac or skeletal muscle. AMPKγ2 mutations cause hypertrophic cardiomyopathy with glycogen deposition and conduction abnormalities; mutations in AMPKγ3 result in increased skeletal muscle glycogen. In order to gain further insight into the roles of the different γ subunits in muscle and into possible disease mechanisms, we localised the γ2 and γ3 subunits, along with the more abundant γ1 subunit, by immunofluorescence in cardiomyocytes and skeletal muscle fibres. The predominant cardiac γ2 variant, γ2-3B, gave a striated pattern in cardiomyocytes, aligning with the Z-disk but with punctate staining similar to T-tubule (L-type Ca2+ channel) and sarcoplasmic reticulum (SERCA2) markers. In skeletal muscle fibres AMPKγ3 localises to the I band, presenting a uniform staining that flanks the Z-disk, also coinciding with the position of Ca2+ influx in these muscles. The localisation of γ2-3B- and γ3-containing AMPK suggests that these trimers may have similar functions in the different muscles. AMPK containing γ2-3B was detected in oxidative skeletal muscles which had low expression of γ3, confirming that these two regulatory subunits may be co-ordinately regulated in response to metabolic requirements. Compartmentalisation of AMPK complexes is most likely dependent on the regulatory γ subunit and this differential localisation may direct substrate selection and specify particular functional roles.