The expression of prolyl isomerase Pin1 is expanded in the skin of patients with atopic dermatitis and facilitates IL-33 expression in HaCaT cells.

Atopic dermatitis (AD) is attributable to both a genetic predisposition and environmental factors. Among numerous cytokines involved in the pathogenesis of AD, interleukin-33 (IL-33), reportedly escaping exocytotically in response to a scratch, is abundantly expressed in the skin tissues of patients with AD and is postulated to induce inflammatory and autoimmune responses. In this study, we first demonstrated that peptidylprolyl cis/trans isomerase, NIMA-interacting 1 (Pin1), a unique enzyme which isomerizes the proline residues of target proteins, is abundantly expressed in keratinocytes, and that the areas where it is present in the skin tissues of AD patients became expanded due to hyperkeratosis. Thus, we investigated the effects of Pin1 on the regulation of IL-33 expression using the human keratinocyte cell line HaCaT. Interestingly, silencing of the Pin1 gene or treatment with Pin1 inhibitors dramatically reduced IL-33 expressions in HaCaT cells, although Pin1 overexpression did not elevate it. Subsequently, we showed that Pin1 binds to STAT1 and the nuclear factor-kappaB (NF-κB) subunit p65. Silencing the Pin1 gene with small interfering RNAs significantly reduced the phosphorylation of p65, while no marked effects of Pin1 on the STAT1 pathway were detected. Thus, it is likely that Pin1 contributes to increased expression of IL-33 via the NF-κB subunit p65 in HaCaT cells, at least modestly. Nevertheless, further study is necessary to demonstrate the pathogenic roles of Pin1 and IL-33 in AD development.

Prolyl isomerase Pin1 promotes extracellular matrix production in hepatic stellate cells through regulating formation of the Smad3-TAZ complex.

Hepatic stellate cells (HSCs) produce extracellular matrixes (ECMs), such as collagen and fibronectin, in response to stimulation with transforming growth factor ß (TGFß). The massive ECM accumulation in the liver due to HSCs causes fibrosis which eventually leads to hepatic cirrhosis and hepatoma development. However, details of the mechanisms underlying continuous HSC activation are as yet poorly understood. We thus attempted to elucidate the role of Pin1, one of the prolyl isomerases, in the underlying mechanism(s), using the human HSC line LX-2. Treatment with Pin1 siRNAs markedly alleviated the TGFß-induced expressions of ECM components such as collagen 1a1/2, smooth muscle actin and fibronectin at both the mRNA and the protein level. Pin1 inhibitors also decreased the expressions of fibrotic markers. In addition, it was revealed that Pin1 associates with Smad2/3/4, and that four Ser/Thr-Pro motifs in the linker domain of Smad3 are essential for binding with Pin1. Pin1 significantly regulated Smad-binding element transcriptional activity without affecting Smad3 phosphorylations or translocation. Importantly, both Yes-associated protein (YAP) and WW domain-containing transcription regulator (TAZ) also participate in ECM induction, and upregulate Smad3 activity rather than TEA domain transcriptional factor transcriptional activity. Although Smad3 interacts with both TAZ and YAP, Pin1 facilitates the Smad3 association with TAZ, but not that with YAP. In conclusion, Pin1 plays pivotal roles in ECM component productions in HSCs through regulation of the interaction between TAZ and Smad3, and Pin1 inhibitors may have the potential to ameliorate fibrotic diseases.

Par14 interacts with the androgen receptor, augmenting both its transcriptional activity and prostate cancer proliferation.

BACKGROUND: Prostate cancer (PCa) is a major cause of cancer morbidity and mortality for men globally, and androgen signaling clearly drives its onset and progression. Androgen receptor (AR) regulation is complex and remains elusive, despite several studies tackling these issues. Therefore, elucidating the mechanism(s) underlying AR regulation is a potentially promising approach to suppressing PCa. METHODS: We report that Par14, one isoform of the prolyl isomerases homologous to Pin1, is a critical regulator of AR transcriptional activity and is essential for PCa cell growth. RESULTS: Par14 was shown to be overexpressed in PCa, based on analyses of deposited data. Importantly, overexpression of Par14 significantly enhanced androgen-sensitive LNCap cell growth. In contrast, silencing of Par14 dramatically decreased cell growth in LNCap cells by causing cell cycle arrest. Mechanistically, silencing of the Par14 gene dramatically induced cyclin-dependent kinase inhibitor p21 at both the mRNA and the protein level through modulating the localization of p53. In addition, suppression of Par14 in LNCap cells was shown to downregulate the expressions of androgen response genes, at both the mRNA and the protein level, induced by dihydrotestosterone. Par14 was shown to directly associate with AR in nuclei via its DNA-binding domain and augment AR transcriptional activity. CONCLUSION: Thus, Par14 plays a critical role in PCa progression, and its enhancing effects on AR signaling are likely to be involved in the underlying molecular mechanisms. These findings suggest Par14 to be a promising therapeutic target for PCa.

Prolyl isomerase Pin1 interacts with adipose triglyceride lipase and negatively controls both its expression and lipolysis.

BACKGROUND: Lipolysis is essential for the supply of nutrients during fasting, the control of body weight, and remodeling of white adipose tissues and thermogenesis. In the obese state, lipolysis activity and the expression of adipose triglyceride lipase (ATGL), a rate-limiting enzyme, is suppressed. However, the mechanism underlying the regulation of ATGL remains largely unknown. We previously reported that a high-fat diet obviously increases protein levels of the prolyl isomerase, Pin1, in epididymal white adipose tissue (epiWAT) of mice and that Pin1 KO mice are resistant to developing obesity. RESULTS: The present study found that deletion of the Pin1 gene in epiWAT upregulated lipolysis and increased ATGL protein expression by ~2-fold. In addition, it was demonstrated that Pin1 directly associated with ATGL and enhanced its degradation through the ubiquitin proteasome system. Indeed, Pin1 overexpression decreased ATGL expression levels, whereas Pin1 knockdown by siRNA treatment upregulated ATGL protein levels without altering mRNA levels. Moreover, under a high fat diet (HFD)-fed condition, adipocyte-specific Pin1 KO (adipoPin1 KO) mice had 2-fold increase lipolytic activity and upregulated ß-oxidation-related gene expressions. These mice also gained less body weight, and had better glucose metabolism according to the results of glucose and insulin tolerance tests. CONCLUSION: Taken together, these results showed that Pin1 directly interacted with and degraded ATGL via a ubiquitin-proteasome system, consequently causing the downregulation of lipolysis. Therefore, Pin1 could be considered a target for the treatment of dyslipidemia and related disorders.