G protein-coupled receptors (GPCRs) are critical for cardiovascular physiology. Cardiac cells express >100 nonchemosensory GPCRs, indicating that important physiological and potential therapeutic targets remain to be discovered. Moreover, there is a growing appreciation that members of the large, distinct taste and odorant GPCR families have specific functions in tissues beyond the oronasal cavity, including in the brain, gastrointestinal tract and respiratory system. To date, these chemosensory GPCRs have not been systematically studied in the heart. We performed RT-qPCR taste receptor screens in rodent and human heart tissues that revealed discrete subsets of type 2 taste receptors (TAS2/Tas2) as well as Tas1r1 and Tas1r3 (comprising the umami receptor) are expressed. These taste GPCRs are present in cultured cardiac myocytes and fibroblasts, and by in situ hybridization can be visualized across the myocardium in isolated cardiac cells. Tas1r1 gene-targeted mice (Tas1r1Cre/Rosa26tdRFP) strikingly recapitulated these data. In vivo taste receptor expression levels were developmentally regulated in the postnatal period. Intriguingly, several Tas2rs were upregulated in cultured rat myocytes and in mouse heart in vivo following starvation. The discovery of taste GPCRs in the heart opens an exciting new field of cardiac research. We predict that these taste receptors may function as nutrient sensors in the heart.

Methadone is a racemic compound composed of the R-form and S-form enantiomers. The drug is usually used in maintenance therapy for the heroin-addicted patients. In our previous study, we found that the cytochrome P-450 (CYP) isozyme 2B6 preferentially metabolizes the S-methadone enantiomer. We thus tested whether CYP2B6 gene polymorphisms had any influence on the concentration or clearance of methadone. Ten single nucleotide polymorphisms within this gene region were evaluated in 366 patients undergoing methadone maintenance for at least 3 months. The plasma steady-state levels of racemic methadone and its metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine were then measured in these individuals. The rs10403955 (T allele in intron 1), rs3745274 (G allele in exon 4), rs2279345 (T allele in intron 5), and rs707265 (A allele in exon 9) CYP2B6 allele types were found to be significantly associated with a higher clearance, a lower plasma concentration, and a lower concentration-to-dosage (C/D) ratio of (S)-methadone (P < 0.0017). Two haplotype blocks of a trinucleotide haplotype (rs8100458-rs10500282-rs10403955 in intron 1) and a hexanucleotide haplotype (rs2279342-rs3745274-rs2279343-rs2279345-rs1038376-rs707265 from intron 2 to exon 9) were constructed within CYP2B6. The major combinations of T-T-T and A-G-A-T-A-A of these particular haplotypes showed significant associations with the plasma concentrations of S-methadone and its C/D ratio (P < 0.0001, respectively). We conclude that genetic polymorphisms in the CYP2B6 gene may therefore be indicators of the clearance, plasma concentration and C/D ratio of S-methadone.

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Our results indicated that downregulation of TS and DHFR genes and upregulation of p21, p27, Lcn-2, and nm23-H1 genes may serve as new biomarkers for predicting responsiveness to pemetrexed.

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Mitochondrial aging, which results in mitochondrial dysfunction, is strongly linked to many age-related diseases. Aging is associated with mitochondrial enlargement and transport of cytosolic proteins into mitochondria. The underlying homeostatic mechanisms that regulate mitochondrial morphology and function, and their breakdown during aging, remain unclear. Here, we identify a mitochondrial protein trafficking pathway in Drosophila melanogaster involving the mitochondria-associated protein Dosmit. Dosmit induces mitochondrial enlargement and the formation of double-membraned vesicles containing cytosolic protein within mitochondria. The rate of vesicle formation increases with age. Vesicles originate from the outer mitochondrial membrane as observed by tracking Tom20 localization, and the process is mediated by the mitochondria-associated Rab32 protein. Dosmit expression level is closely linked to the rate of ubiquitinated protein aggregation, which are themselves associated with age-related diseases. The mitochondrial protein trafficking route mediated by Dosmit offers a promising target for future age-related mitochondrial disease therapies.

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Abstract-Major interest surrounds how angiotensin II triggers cardiac hypertrophy via epidermal growth factor receptor transactivation. G protein-mediated transduction, angiotensin type 1 receptor phosphorylation at tyrosine 319, and ␤-arrestin-dependent scaffolding have been suggested, yet the mechanism remains controversial. We examined these pathways in the most reductionist model of cardiomyocyte growth, neonatal ventricular cardiomyocytes. Analysis with [ 32 P]-labeled cardiomyocytes, wild-type and [Y319A] angiotensin type 1 receptor immunoprecipitation and phosphorimaging, phosphopeptide analysis, and antiphosphotyrosine blotting provided no evidence for tyrosine phosphorylation at Y319 or indeed of the receptor, and mutation of Y319 (to A/F) did not prevent either epidermal growth factor receptor transactivation in COS-7 cells or cardiomyocyte hypertrophy. Instead, we demonstrate that transactivation and cardiomyocyte hypertrophy are completely abrogated by loss of G-protein coupling, whereas a constitutively active angiotensin type 1 receptor mutant was sufficient to trigger transactivation and growth in the absence of ligand. These results were supported by the failure of the ␤-arrestin-biased ligand SII angiotensin II to transactivate epidermal growth factor receptor or promote hypertrophy, whereas a ␤-arrestin-uncoupled receptor retained these properties. We also found angiotensin II-mediated cardiomyocyte hypertrophy to be attenuated by a disintegrin and metalloprotease inhibition. Thus, G-protein coupling, and not Y319 phosphorylation or ␤-arrestin scaffolding, is required for epidermal growth factor receptor transactivation and cardiomyocyte hypertrophy via the angiotensin type 1 receptor. A ngiotensin II (Ang II) contributes to progression of left ventricular hypertrophy, a major independent risk factor for myocardial infarction and sudden death, 1 yet the molecular mechanisms governing cardiac hypertrophy remain controversial. Recently, a new paradigm for Ang II hypertrophy has emerged. We and others have shown that angiotensin type 1 receptors (AT 1 Rs) hijack the epidermal growth factor (EFR) receptor (EGFR) via a process termed the "triple membrane-passing signaling paradigm of EGFR transactivation." 2-5 More specifically, AT 1 R activation causes metalloprotease-dependent EGF-like ligand release and subsequent EGFR binding to initiate hypertrophic signaling cascades. Yet the process is likely more complicated: multiple G protein-coupled receptor (GPCR) signals, a disintegrin and metalloproteases (ADAMs), EGF-like ligands, and EGFR subtypes have been implicated in this process. 2 A major focus of Ang II research is the mechanism by which the AT 1 R signals to the EGFR. Recent studies suggested a G protein-independent pathway for growth activation, 6 -9 despite evidence that G␣ q/11 , a heterotrimeric G protein that couples to the AT 1 R, is essential for hypertrophy. 10 Indeed, others indicate that G-protein coupling to AT 1 R is required for EGFR transactivation in COS-7 and vascular smoot...