Receptor-mediated Gq signaling promotes hypertrophic growth of cultured neonatal rat cardiac myocytes and is postulated to transduce in vivo cardiac pressure overload hypertrophy. Although initially compensatory, hypertrophy can proceed by unknown mechanisms to cardiac failure. We used adenoviral infection and transgenic overexpression of the alpha subunit of Gq to autonomously activate Gq signaling in cardiomyocytes. In cultured cardiac myocytes, overexpression of wild-type G␣q resulted in hypertrophic growth. Strikingly, expression of a constitutively activated mutant of G␣q, which further increased Gq signaling, produced initial hypertrophy, which rapidly progressed to apoptotic cardiomyocyte death. This paradigm was recapitulated during pregnancy in G␣q overexpressing mice and in transgenic mice expressing high levels of wild-type G␣q. The consequence of cardiomyocyte apoptosis was a transition from compensated hypertrophy to a rapidly progressive and lethal cardiomyopathy. Progression from hypertrophy to apoptosis in vitro and in vivo was coincident with activation of p38 and Jun kinases. These data suggest a mechanism in which moderate levels of Gq signaling stimulate cardiac hypertrophy whereas high level Gq activation results in cardiomyocyte apoptosis. The identification of a single biochemical stimulus regulating cardiomyocyte growth and death suggests a plausible mechanism for the progression of compensated hypertrophy to decompensated heart failure.

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Expression of platelet thromboxane receptors is transcriptionally increased during megakaryocytic differentiation stimulated by phorbol 12-myristate 13-acetate (PMA). We previously cloned and characterized the promoter region of the human thromboxane receptor gene and localized PMA-responsive elements to a region between 1.84 and 1.95 kilobase pairs (kb) 5 of the transcription initiation site (D'Angelo, D. D., Davis, M. G., Houser, W. A., Eubank, J. J., Ritchie, M. E., and Dorn, G. W., II (1995) Circ. Res. 77, 466 -474). Herein we report the localization of the PMA response element to a 14-nucleotide C-rich sequence, flanked by an octanucleotide inverted repeat, located ؊1.938 to ؊1.925 kb 5 of the transcription start site of this gene. We further identify the PMA-responsive enhancer factor that binds to this Crich sequence as Sp1. Heterologous thromboxane receptor gene promoter/thymidilate kinase reporter constructs transfected into K562 cells exhibited PMA responsiveness when the C-rich element was included with additional 3 sequence from ؊1.924 to ؊1.84 kb. However, mutations of the C-rich element that disrupted a GC box located on the inverse strand eliminated PMA responsiveness and, in gel mobility shift assays, eliminated binding of Sp1. PMA treatment of K562 cells significantly increased, by 5-fold, Sp1 binding to the C-rich element and increased both phosphorylated and nonphosphorylated Sp1 protein levels by 2-fold. Furthermore, PMA treatment transiently increased Sp1 mRNA levels prior to increasing thromboxane receptor mRNA, suggesting that up-regulation of Sp1 contributes to up-regulation of thromboxane receptors. Finally, we have detected an unidentified K562 nuclear protein that binds specifically to the sense strand of the C-rich sequence overlapping the Sp1 binding site and that, by stabilizing a double stem-loop conformation of this DNA segment, may also play a role in Sp1 regulation of this gene. These studies are the first to describe regulatory and regulated roles for Sp1 in PMA-responsive gene expression and suggest that modulation of Sp1 levels controls thromboxane receptor expression during megakaryocytic differentiation.Thromboxane A 2 is one of the most potent platelet-aggregating and vasoconstricting substances known and is crucial for maintenance of normal hemostasis (1). While considerable attention has been directed toward measuring increased thromboxane production in various disease states including acute coronary ischemic syndromes (2, 3), relatively little is known about how target tissue responses to thromboxane may be modulated. Two intriguing studies have reported increased numbers of platelet thromboxane receptors, with enhanced platelet aggregation, in acute myocardial infarction and unstable angina pectoris (4, 5). The observation that this thromboxane receptor abnormality was reversible after acute myocardial infarction (4) and the discovery of an identical abnormality in patients with unstable angina (the clinical precursor of completed myocardial infarct) (5), strongly sugg...

Hair from different individuals can be distinguished by physical properties. Although some data exist on other species, examination of the individual molecular differences within the human hair shaft has not been thoroughly investigated. Shotgun proteomic analysis revealed considerable variation in profile among samples from Caucasian, African–American, Kenyan and Korean subjects. Within these ethnic groups, prominent keratin proteins served to distinguish individual profiles. Differences between ethnic groups, less marked, relied to a large extent on levels of keratin associated proteins. In samples from Caucasian subjects, hair shafts from axillary, beard, pubic and scalp regions exhibited distinguishable profiles, with the last being most different from the others. Finally, the profile of isolated hair cuticle cells was distinguished from that of total hair shaft by levels of more than 20 proteins, the majority of which were prominent keratins. The cuticle also exhibited relatively high levels of epidermal transglutaminase (TGM3), accounting for its observed low degree of protein extraction by denaturants. In addition to providing insight into hair structure, present findings may lead to improvements in differentiating hair from various ethnic origins and offer an approach to extending use of hair in crime scene evidence for distinguishing among individuals.