Now showing 1 - 2 of 2
  • Publication
    Identification of an interaction between the TPalpha and TPbeta isoforms of the human thromboxane A2 receptor with protein kinase C-related kinase (PRK) 1 : implications for prostate cancer.
    In humans, thromboxane (TX)A2 signals through the TPalpha and TPbeta isoforms of the TXA2 receptor, or TP. Herein, the RhoA effector protein kinase C-related kinase (PRK) 1 was identified as an interactant of both TPalpha and TPbeta involving common and unique sequences within their respective carboxyl-terminal (C)-tail domains and the kinase domain of PRK1 (PRK1640-942). While the interaction with PRK1 is constitutive, agonist-activation of TPalpha/TPbeta did not regulate the complex per se but enhanced PRK1 activation leading to phosphorylation of its general substrate histone H1 in vitro. Altered PRK1 and TP expression and signalling are increasingly implicated in certain neoplasms, particularly in androgen-associated prostate carcinomas. Agonist-activation of TPalpha/TPbeta led to phosphorylation of histone H3 at Thr11 (H3Thr11), a previously recognized specific marker of androgen induced-chromatin remodeling, in the prostate LNCaP and PC-3 cell lines but not in primary vascular smooth muscle or endothelial cells. Moreover, this effect was augmented by dihydrotestosterone in androgen-responsive LNCaP but not in non-responsive PC-3 cells. Furthermore, PRK1 was confirmed to constitutively interact with TPalpha/TPbeta in both LNCaP and PC-3 cells and targeted disruption of PRK1 impaired TPalpha/TPbeta-mediated H3Thr11 phosphorylation in, and cell migration of, both prostate cell types. Collectively, considering the role of TXA2 as a potent mediator of RhoA signalling, the identification of PRK1 as a bone fide interactant of TPalpha/TPbeta, and leading to H3Thr11 phosphorylation to regulate cell migration, has broad functional significance such as within the vasculature and in neoplasms in which both PRK1 and the TPs are increasingly implicated.
      269Scopus© Citations 24
  • Publication
    Differential regulation of RhoA-mediated signaling by the TPalpha and TPbeta isoforms of the human thromboxane A2 receptor : independent modulation of TPalpha signaling by prostacyclin and nitric oxide
    In humans, thromboxane (TX) A2 signals through the TPalpha and TPbeta isoforms of the TXA2 receptor that exhibit common and distinct roles. For example, Gq/phospholipase (PL)Cbeta signaling by TPalpha is directly inhibited by the vasodilators prostacyclin and nitric oxide (NO) whereas that signaling by TPbeta is unaffected. Herein, we investigated whether TPalpha and/or TPbeta regulate G12/Rho activation and whether that signaling might be differentially regulated by prostacyclin and/or NO. Both TPalpha and TPbeta independently regulated RhoA activation and signaling in clonal cells over-expressing TPalpha or TPbeta and in primary human aortic smooth muscle cells (1o AoSMCs). While RhoA- signaling by TPalpha was directly impaired by prostacyclin and NO through protein kinase (PK)A- and PKG-dependent phosphorylation, respectively, signaling by TPbeta was not directly affected by either agent. Collectively, while TPalpha and TPbeta contribute to RhoA activation, our findings support the hypothesis that TPalpha is involved in the dynamic regulation of haemostasis and vascular tone, such as in response to prostacyclin and NO. Conversely, the role of TPbeta in such processes remains unsolved. Data herein provide essential new insights into the physiologic roles of TPalpha and TPbeta and, through studies in AoSMCs, reveal an additional mode of regulation of VSM contractile responses by TXA2.
    Scopus© Citations 35  612