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Regulation of KLF4 turnover reveals an unexpected tissue-specific role of pVHL in tumorigenesis.

ABSTRACT: The transcription factor Krüppel-like factor 4 (KLF4) is an important regulator of cell-fate decision, including cell-cycle regulation, apoptosis, and stem cell renewal, and plays an ambivalent role in tumorigenesis as a tissue-specific tumor suppressor or oncogene. Here, we report that the Von Hippel-Lindau gene product, pVHL, physically interacts with KLF4 and regulates its rapid turnover observed in both differentiated and stem cells. We provide mechanistic insights into KLF4 degradation and show that pVHL depletion in colorectal cancer cells leads to cell-cycle arrest concomitant with increased transcription of the KLF4-dependent p21 gene. Finally, immunohistochemical staining revealed elevated pVHL and reduced KLF4 levels in colon cancer tissues. We therefore propose that unexpectedly pVHL, via the degradation of KLF4, is a facilitating factor in colorectal tumorigenesis.

SUBMITTER: Gamper AM

PROVIDER: S-EPMC3982234 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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Regulation of KLF4 turnover reveals an unexpected tissue-specific role of pVHL in tumorigenesis.

Gamper Armin M AM Qiao Xinxian X Kim Jennifer J Zhang Liyong L DeSimone Michelle C MC Rathmell W Kimryn WK Wan Yong Y

Molecular cell 20120101 2

The transcription factor Krüppel-like factor 4 (KLF4) is an important regulator of cell-fate decision, including cell-cycle regulation, apoptosis, and stem cell renewal, and plays an ambivalent role in tumorigenesis as a tissue-specific tumor suppressor or oncogene. Here, we report that the Von Hippel-Lindau gene product, pVHL, physically interacts with KLF4 and regulates its rapid turnover observed in both differentiated and stem cells. We provide mechanistic insights into KLF4 degradation and ...[more]

PMID: 22284679

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Project description:Recent smooth muscle cell (SMC) lineage-tracing studies have revealed that SMCs undergo remarkable changes in phenotype during development of atherosclerosis. Of major interest, we demonstrated that Kruppel-like factor 4 (KLF4) in SMCs is detrimental for overall lesion pathogenesis, in that SMC-specific conditional knockout of the KLF4 gene ( Klf4) resulted in smaller, more-stable lesions that exhibited marked reductions in the numbers of SMC-derived macrophage- and mesenchymal stem cell-like cells. However, since the clinical consequences of atherosclerosis typically occur well after our reproductive years, we sought to identify beneficial KLF4-dependent SMC functions that were likely to be evolutionarily conserved. We tested the hypothesis that KLF4-dependent SMC transitions play an important role in the tissue injury-repair process. Using SMC-specific lineage-tracing mice positive and negative for simultaneous SMC-specific conditional knockout of Klf4, we demonstrate that SMCs in the remodeling heart after ischemia-reperfusion injury (IRI) express KLF4 and transition to a KLF4-dependent macrophage-like state and a KLF4-independent myofibroblast-like state. Moreover, heart failure after IRI was exacerbated in SMC Klf4 knockout mice. Surprisingly, we observed a significant cardiac dilation in SMC Klf4 knockout mice before IRI as well as a reduction in peripheral resistance. KLF4 chromatin immunoprecipitation-sequencing analysis on mesenteric vascular beds identified potential baseline SMC KLF4 target genes in numerous pathways, including PDGF and FGF. Moreover, microvascular tissue beds in SMC Klf4 knockout mice had gaps in lineage-traced SMC coverage along the resistance arteries and exhibited increased permeability. Together, these results provide novel evidence that Klf4 has a critical maintenance role within microvascular SMCs: it is required for normal SMC function and coverage of resistance arteries. NEW & NOTEWORTHY We report novel evidence that the Kruppel-like factor 4 gene ( Klf4) has a critical maintenance role within microvascular smooth muscle cells (SMCs). SMC-specific Klf4 knockout at baseline resulted in a loss of lineage-traced SMC coverage of resistance arteries, dilation of resistance arteries, increased blood flow, and cardiac dilation.

Project description:Recent smooth muscle cell (SMC) lineage tracing studies have demonstrated that SMCs undergo remarkable changes in phenotype during development of atherosclerosis, including loss of typical SMC markers such as ACTA2 and Klf4 dependent activation of multiple markers of macrophages and mesenchymal stem cells. Of major interest, we showed Klf4 in SMC is critical for overall lesion pathogenesis as SMC-specific conditional knockout (KO) of Klf4 resulted in smaller, more stable lesions that exhibited marked reductions in the numbers of SMC-derived macrophage-like and mesenchymal stem cell like cells. Herein we tested the hypothesis that Klf4 dependent SMC transitions are beneficial following myocardial infarction (MI). Utilizing SMC-specific lineage tracing mice +/- simultaneous SMC-specific conditional KO of Klf4, we demonstrate that SMCs express Klf4 and transition to a Klf4 dependent macrophage-like state as well as a Klf4 independent myofibroblast-like state. SMC specific, conditional KO of Klf4 resulted in marked exacerbation of heart failure following MI. Surprisingly, significant cardiac dilation was seen in SMC-Klf4 KO mice prior to MI. This cardiac dilation was accompanied by a reduction in peripheral resistance, as evidenced by a reduction in blood pressure, an increase in blood flow, and a larger passive diameter of mesenteric resistance arteries as measured by pressure myography. Klf4 ChIP-Seq analysis on the mesenteric resistance arteries identified potential Klf4 target genes in SMC at baseline in pathways including PDGF and FGF signaling previously shown to be important for perivascular cell investment. Interestingly, examination of microvascular tissue beds revealed gaps in lineage traced SMC coverage along the resistance arteries. Taken together, these results provide novel evidence that Klf4 has a critical maintenance role within microvascular SMCs, including being required for normal SMC coverage of resistance arteries as well as their function.

Dataset Information

Regulation of KLF4 turnover reveals an unexpected tissue-specific role of pVHL in tumorigenesis.

Publications

Regulation of KLF4 turnover reveals an unexpected tissue-specific role of pVHL in tumorigenesis.

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