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Richard L Eckert - One of the best experts on this subject based on the ideXlab platform.
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protein kinase c δ increases kruppel like factor 4 protein which drives Involucrin gene transcription in differentiating keratinocytes
Journal of Biological Chemistry, 2013Co-Authors: Yap Ching Chew, Gautam Adhikary, Gerald M Wilson, Richard L EckertAbstract:KLF4 is a member of the Kruppel-like factor family of transcriptional regulators. KLF4 has been shown to be required for normal terminal differentiation of keratinocytes, but the molecular mechanism whereby KLF4 regulates genes associated with the differentiation process has not been studied. In the present study, we explore the impact of KLF4 on expression of Involucrin, a gene that is specifically expressed in differentiated keratinocytes. KLF4 overexpression and knockdown studies show that Involucrin mRNA and protein level correlates directly with KLF4 level. Moreover, studies of mutant KLF4 proteins indicate that transcriptionally inactive forms do not increase Involucrin expression. PKCδ is a regulator of keratinocyte differentiation that increases expression of differentiation-associated target genes, including Involucrin. Overexpression of KLF4 augments the PKCδ-dependent increase in Involucrin expression, whereas KLF4 knockdown attenuates this response. The KLF4 induction of human Involucrin (hINV) promoter activity is mediated via KLF4 binding to a GC-rich element located in the hINV promoter distal regulatory region, a region of the promoter required for in vivo Involucrin expression. Mutation of the GC-rich element, an adjacent AP1 factor binding site, or both sites severely attenuates the response. Moreover, loss of KLF4 in an epidermal equivalent model of differentiation results in loss of hINV expression. These studies suggest that KLF4 is part of a multiprotein complex that interacts that the hINV promoter distal regulatory region to drive differentiation-dependent hINV gene expression in epidermis.
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The distal and proximal regulatory regions of the Involucrin gene promoter have distinct functions and are required for in vivo Involucrin expression.
Journal of Investigative Dermatology, 2006Co-Authors: James F Crish, Ramamurthy Gopalakrishnan, Frederic Bone, Anita C. Gilliam, Richard L EckertAbstract:Involucrin is a marker of human keratinocyte differentiation. Previous studies show that the human Involucrin gene promoter has two distinct regulatory regions – the proximal regulatory region (PRR) and the distal regulatory region (DRR). To study the role of these regions in vivo, we have constructed human Involucrin promoter transgenic mice and monitored the impact of specific promoter mutations on Involucrin gene expression. In this study, we monitor the impact of specific mutations on expression in a range of surface epithelia. We begin by confirming previous observations made in footpad epidermis by showing that the full-length Involucrin promoter drives differentiation-appropriate expression in other surface epithelia, including epidermis, cervix, and esophagus. We further show that mutation of the activator protein AP1-5 site in the DRR completely eliminates transgene expression in all of these tissues. In contrast, mutation of the DRR Sp1 site reduces overall expression, but does not alter the differentiation dependence. Additional studies identify a DRR immediate suprabasal element (ISE). Deletion of the ISE results in a loss of transgene expression in the immediate suprabasal layers. Our studies also indicate that the PRR is important for appropriate transgene expression. Mutation of a PRR C/EBP (CCAAT enhancer binding protein) transcription factor binding site results in patchy/discontinuous expression. These studies suggest that AP1, Sp1, and C/EBP transcription factors are required for appropriate differentiation-dependent Involucrin expression, and that the mechanism of regulation is similar in most surface epithelia.
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regulation of Involucrin expression in normal human corneal epithelial cells a role for activator protein one
Investigative Ophthalmology & Visual Science, 2004Co-Authors: Gautam Adhikary, James F Crish, Jonathan H Lass, Richard L EckertAbstract:PURPOSE. Understanding the mechanisms that regulate gene expression in the human cornea is an important goal. In the present study, the Involucrin gene was used as a model to study this regulation. Human Involucrin (hINV) is a structural protein that is selectively expressed in surface epithelia, including corneal epithelial cells. METHODS. Regulation of Involucrin gene expression was monitored in cultures of normal human primary corneal epithelial cells. RESULTS. The studies revealed that an activator protein (AP)-1 DNA-binding site is essential for appropriate basal and stimulus-dependent hINV promoter activity. Mutation of this site, AP1-1, results in a loss of hINV promoter activity. A gel mobility supershift analysis revealed interaction of the AP1 factors, Fra-1, Fra-2, and JunB, with this element. Inhibition of API function with a dominant-negative form of API also inhibited expression. Treatment with 12-O-tetradecanoylphorbol-13-ace-tate (TPA), a protein kinase C activator, increased hINV gene expression, a response that correlates with increased nuclear API factor level and binding to the hINV gene AP1-1 response element. Expression of the endogenous hINV gene is also increased by TPA treatment. CONCLUSIONS. These findings point to an important role for API transcription factors in the regulation of human corneal epithelial cell Involucrin gene expression.
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Regulation of Involucrin Gene Expression
Journal of Investigative Dermatology, 2004Co-Authors: Richard L Eckert, James F Crish, Gautam Adhikary, Ramamurthy Gopalakrishnan, Frederic Bone, Tatiana Efimova, Shervin R. Dashti, Anne Deucher, Guosheng Huang, Sivaprakasam BalasubramanianAbstract:The epidermis is a dynamic renewing structure that provides life-sustaining protection from the environment. The major cell type of the epidermis, the epidermal keratinocyte, undergoes a carefully choreographed program of differentiation. Alteration of these events results in a variety of debilitating and life-threatening diseases. Understanding how this process is regulated is an important current goal in biology. In this review, we summarize the literature regarding regulation of Involucrin, an important marker gene that serves as a model for understanding the mechanisms that regulate the differentiation process. Current knowledge describing the role of transcription factors and signaling cascades in regulating Involucrin gene expression are presented. These studies describe a signaling cascade that includes the novel protein kinase C isoforms, Ras, MEKK1, MEK3, and a p38δ–extracellular signal regulated kinase 1/2 complex. This cascade regulates activator protein one, Sp1, and CCATT/enhancer-binding protein transcription factor DNA binding to two discrete Involucrin promoter regions, the distal- and proximal-regulatory regions, to regulate Involucrin gene expression.
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fos related antigen fra 1 junb and jund activate human Involucrin promoter transcription by binding to proximal and distal ap1 sites to mediate phorbol ester effects on promoter activity
Journal of Biological Chemistry, 1995Co-Authors: Jean F Welter, James F Crish, Chapla Agarwal, Richard L EckertAbstract:Abstract Human Involucrin (hINV) is a cornified envelope precursor that is specifically expressed in the suprabasal epidermal layers. We previously demonstrated that 2500 base pairs of the hINV gene upstream regulatory region confers differentiation appropriate regulation in transgenic mice. An analysis of the hINV gene sequence upstream of the transcription start site reveals five potential AP1 binding sites (AP1-1 to 5). Using reporter gene constructs in human keratinocytes, we show that the most distal (AP1-5) and most proximal (AP1-1) AP1 sites are essential for high level transcriptional activity. Simultaneous mutation of these sites reduces transcription by 80%. Gel supershift experiments indicate the interaction of these sites with Fra-1, junB, and junD. Involucrin mRNA levels increase 10-fold and promoter activity 5-11-fold when differentiation is induced by phorbol ester. Functional studies implicate AP1-1 and AP1-5 in mediating the phorbol ester-dependent increase in promoter activity. No Involucrin promoter activity or Involucrin mRNA was detected in 3T3 fibroblasts. We conclude that (i) two AP1 sites in the hINV promoter are important elements required for keratinocyte-specific expression, (ii) these AP1-1 sites mediate the phorbol ester-dependent increase in promoter activity, and (iii) Fra-1, junB, and junD may be important regulators of hINV expression in epidermis.
James F Crish - One of the best experts on this subject based on the ideXlab platform.
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The distal and proximal regulatory regions of the Involucrin gene promoter have distinct functions and are required for in vivo Involucrin expression.
Journal of Investigative Dermatology, 2006Co-Authors: James F Crish, Ramamurthy Gopalakrishnan, Frederic Bone, Anita C. Gilliam, Richard L EckertAbstract:Involucrin is a marker of human keratinocyte differentiation. Previous studies show that the human Involucrin gene promoter has two distinct regulatory regions – the proximal regulatory region (PRR) and the distal regulatory region (DRR). To study the role of these regions in vivo, we have constructed human Involucrin promoter transgenic mice and monitored the impact of specific promoter mutations on Involucrin gene expression. In this study, we monitor the impact of specific mutations on expression in a range of surface epithelia. We begin by confirming previous observations made in footpad epidermis by showing that the full-length Involucrin promoter drives differentiation-appropriate expression in other surface epithelia, including epidermis, cervix, and esophagus. We further show that mutation of the activator protein AP1-5 site in the DRR completely eliminates transgene expression in all of these tissues. In contrast, mutation of the DRR Sp1 site reduces overall expression, but does not alter the differentiation dependence. Additional studies identify a DRR immediate suprabasal element (ISE). Deletion of the ISE results in a loss of transgene expression in the immediate suprabasal layers. Our studies also indicate that the PRR is important for appropriate transgene expression. Mutation of a PRR C/EBP (CCAAT enhancer binding protein) transcription factor binding site results in patchy/discontinuous expression. These studies suggest that AP1, Sp1, and C/EBP transcription factors are required for appropriate differentiation-dependent Involucrin expression, and that the mechanism of regulation is similar in most surface epithelia.
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regulation of Involucrin expression in normal human corneal epithelial cells a role for activator protein one
Investigative Ophthalmology & Visual Science, 2004Co-Authors: Gautam Adhikary, James F Crish, Jonathan H Lass, Richard L EckertAbstract:PURPOSE. Understanding the mechanisms that regulate gene expression in the human cornea is an important goal. In the present study, the Involucrin gene was used as a model to study this regulation. Human Involucrin (hINV) is a structural protein that is selectively expressed in surface epithelia, including corneal epithelial cells. METHODS. Regulation of Involucrin gene expression was monitored in cultures of normal human primary corneal epithelial cells. RESULTS. The studies revealed that an activator protein (AP)-1 DNA-binding site is essential for appropriate basal and stimulus-dependent hINV promoter activity. Mutation of this site, AP1-1, results in a loss of hINV promoter activity. A gel mobility supershift analysis revealed interaction of the AP1 factors, Fra-1, Fra-2, and JunB, with this element. Inhibition of API function with a dominant-negative form of API also inhibited expression. Treatment with 12-O-tetradecanoylphorbol-13-ace-tate (TPA), a protein kinase C activator, increased hINV gene expression, a response that correlates with increased nuclear API factor level and binding to the hINV gene AP1-1 response element. Expression of the endogenous hINV gene is also increased by TPA treatment. CONCLUSIONS. These findings point to an important role for API transcription factors in the regulation of human corneal epithelial cell Involucrin gene expression.
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Regulation of Involucrin Gene Expression
Journal of Investigative Dermatology, 2004Co-Authors: Richard L Eckert, James F Crish, Gautam Adhikary, Ramamurthy Gopalakrishnan, Frederic Bone, Tatiana Efimova, Shervin R. Dashti, Anne Deucher, Guosheng Huang, Sivaprakasam BalasubramanianAbstract:The epidermis is a dynamic renewing structure that provides life-sustaining protection from the environment. The major cell type of the epidermis, the epidermal keratinocyte, undergoes a carefully choreographed program of differentiation. Alteration of these events results in a variety of debilitating and life-threatening diseases. Understanding how this process is regulated is an important current goal in biology. In this review, we summarize the literature regarding regulation of Involucrin, an important marker gene that serves as a model for understanding the mechanisms that regulate the differentiation process. Current knowledge describing the role of transcription factors and signaling cascades in regulating Involucrin gene expression are presented. These studies describe a signaling cascade that includes the novel protein kinase C isoforms, Ras, MEKK1, MEK3, and a p38δ–extracellular signal regulated kinase 1/2 complex. This cascade regulates activator protein one, Sp1, and CCATT/enhancer-binding protein transcription factor DNA binding to two discrete Involucrin promoter regions, the distal- and proximal-regulatory regions, to regulate Involucrin gene expression.
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fos related antigen fra 1 junb and jund activate human Involucrin promoter transcription by binding to proximal and distal ap1 sites to mediate phorbol ester effects on promoter activity
Journal of Biological Chemistry, 1995Co-Authors: Jean F Welter, James F Crish, Chapla Agarwal, Richard L EckertAbstract:Abstract Human Involucrin (hINV) is a cornified envelope precursor that is specifically expressed in the suprabasal epidermal layers. We previously demonstrated that 2500 base pairs of the hINV gene upstream regulatory region confers differentiation appropriate regulation in transgenic mice. An analysis of the hINV gene sequence upstream of the transcription start site reveals five potential AP1 binding sites (AP1-1 to 5). Using reporter gene constructs in human keratinocytes, we show that the most distal (AP1-5) and most proximal (AP1-1) AP1 sites are essential for high level transcriptional activity. Simultaneous mutation of these sites reduces transcription by 80%. Gel supershift experiments indicate the interaction of these sites with Fra-1, junB, and junD. Involucrin mRNA levels increase 10-fold and promoter activity 5-11-fold when differentiation is induced by phorbol ester. Functional studies implicate AP1-1 and AP1-5 in mediating the phorbol ester-dependent increase in promoter activity. No Involucrin promoter activity or Involucrin mRNA was detected in 3T3 fibroblasts. We conclude that (i) two AP1 sites in the hINV promoter are important elements required for keratinocyte-specific expression, (ii) these AP1-1 sites mediate the phorbol ester-dependent increase in promoter activity, and (iii) Fra-1, junB, and junD may be important regulators of hINV expression in epidermis.
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tissue specific and differentiation appropriate expression of the human Involucrin gene in transgenic mice an abnormal epidermal phenotype
Differentiation, 1993Co-Authors: James F Crish, Shubha Murthy, Joanne M. Howard, Tarif M. Zaim, Richard L EckertAbstract:Abstract Involucrin is a precursor of the keratinocyte cornified envelope that is specifically expressed in the suprabasal layers of the epidermis and other stratifying squamous epithelia. To study Involucrin gene expression and the function of Involucrin, we expressed a 6 kb DNA fragment of the human Involucrin gene, containing approximately 2.5 kb of upstream sequence and 0.5 kb of downstream sequence, in transgenic mice. The transgene produces a 68 kDa protein that is detected by a human Involucrin-specific antibody, and is expressed in a tissuespecific and differentiation-appropriate manner (i.e., expression is confined to the suprabasal layers of the epidermis, extocervix, trachea, esophagus and conjunctiva). Soluble Involucrin levels are two to four times higher in transgenic epidermal keratinocytes compared to human foreskin keratinocytes. Newborn heterozygous animals have a normal birth weight and a normal appearing epidermis and hair growth begins at 4 to 5 days of age (i.e., the same time as hair growth in non-transgenic animals). In a subpopulation of the newborn homozygous animals birth weight is reduced, the epidermis is scaly and hair growth begins late, at around 9 to 10 days of age. In addition, the hair tends to stand erect on both heterozygous and homozygous adult animals giving the appearance of diffuse alopecia. Immunofluorescent and electron microscopy localize Involucrin in the hair follicle and cornified envelope, respectively. These results suggest that overexpression of Involucrin may cause abnormalities in hair follicle structure/function and cornified envelope structure. These animals provide a new model for the study of cornified envelope structure and function.
Toshimasa Yamauchi - One of the best experts on this subject based on the ideXlab platform.
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stat5a pparγ pathway regulates Involucrin expression in keratinocyte differentiation
Journal of Investigative Dermatology, 2007Co-Authors: Koji Sayama, Sho Tokumaru, Satoshi Hirakawa, Lujun Yang, Kenshi Yamasaki, Yasushi Hanakawa, Yuji Shirakata, Mikiko Tohyama, Xiaoling Wang, Toshimasa YamauchiAbstract:Signal transducers and activators of transcription (STATs) are critical to growth factor-mediated intracellular signal transduction. We observed the rapid expression and activation of STAT5a during keratinocyte differentiation induced by suspension culture. STAT5a expression preceded that of Involucrin, an important molecule in the terminal differentiation of keratinocytes. To determine whether STAT5a regulated Involucrin expression, we expressed a dominant-negative (dn) STAT5a that blocks the dimerization of STAT5 and inhibits its nuclear translocation. We found that dn-STAT5a inhibited Involucrin expression in keratinocytes. Given that STAT5 regulates adipogenesis via activating the peroxisome proliferator-activated receptor (PPAR) γ signal, we hypothesized that STAT5a regulated Involucrin expression in the same manner. To test this hypothesis, we examined the expression and transactivation of PPAR γ in a suspension culture of keratinocytes. Suspension culture induced PPAR γ expression and triggered PPAR γ transactivation rapidly and dn-STAT5a downregulated this induction and suppressed PPAR γ transactivation. Furthermore, preincubation with the PPAR γ /retinoid X-receptor inhibitor HX-531 or the introduction of a dn-PPAR γ prevented the activation of Involucrin promoter and inhibited its induction. This report provides early evidence of a major role for STAT5a in the differentiation of keratinocytes, where it contributes to Involucrin expression by activating the PPAR γ signal.
Koji Sayama - One of the best experts on this subject based on the ideXlab platform.
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PPARγ is an important transcription factor in 1α, 25-dihydroxyvitamin D3-induced Involucrin expression
Journal of Dermatological Science, 2008Co-Authors: Xiuju Dai, Sho Tokumaru, Satoshi Hirakawa, Lujun Yang, Yasushi Hanakawa, Yuji Shirakata, Koji Sayama, Mikiko Tohyama, Koji HashimotoAbstract:Summary Background 1α,25-Dihydroxyvitamin D3 (1α,25(OH)2D3), the active form of vitamin D, suppresses keratinocyte proliferation, promotes keratinocyte differentiation, and induces Involucrin expression. Peroxisome proliferation-activated receptors (PPARs) are ligand-activated transcription factors. It has been reported that PPARs stimulate keratinocyte differentiation and regulate the expression of differentiation molecules. Objective Keratinocytes treated with 1α,25(OH)2D3 induced PPARγ, which was followed by increased Involucrin expression. In this study, we investigated whether PPARγ is involved in the 1α,25(OH)2D3-induced Involucrin expression in human keratinocytes. Methods Subconfluent keratinocytes were treated with 10−7 M 1α,25(OH)2D3 for the indicated times, and PPAR and Involucrin mRNA expression were determined by real-time RT-PCR. The levels of PPARs, Involucrin, p38, and phospho-p38 proteins were assayed by Western blotting, and the DNA binding activities of PPARγ and AP-1 were investigated by electrophoretic mobility shift assays (EMSA). To examine the role of PPARγ in 1α,25(OH)2D3 responses, recombinant adenovirus carrying a dominant-negative form of PPARγ (Axdn-PPARγ) was constructed and transfected into keratinocytes. The p38 inhibitor SB203580 was added to the cultures to evaluate the involvement of p38 in Involucrin expression. Results 1α,25(OH)2D3 induced PPARγ expression and stimulated PPARγ activity. The introduction of dn-PPARγ inhibited the expression of Involucrin mRNA and protein induced by 1α,25(OH)2D3, and suppressed AP-1 DNA binding activity. 1α,25(OH)2D3 also triggered the phosphorylation of p38, which contributes to Involucrin induction. Moreover, dn-PPARγ prevented the 1α,25(OH)2D3-induced phosphorylation of p38. Conclusions These results suggest that PPARγ regulates Involucrin expression by controlling the AP-1 signal and p38 activation in 1α,25(OH)2D3-induced keratinocyte differentiation.
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stat5a pparγ pathway regulates Involucrin expression in keratinocyte differentiation
Journal of Investigative Dermatology, 2007Co-Authors: Koji Sayama, Sho Tokumaru, Satoshi Hirakawa, Lujun Yang, Kenshi Yamasaki, Yasushi Hanakawa, Yuji Shirakata, Mikiko Tohyama, Xiaoling Wang, Toshimasa YamauchiAbstract:Signal transducers and activators of transcription (STATs) are critical to growth factor-mediated intracellular signal transduction. We observed the rapid expression and activation of STAT5a during keratinocyte differentiation induced by suspension culture. STAT5a expression preceded that of Involucrin, an important molecule in the terminal differentiation of keratinocytes. To determine whether STAT5a regulated Involucrin expression, we expressed a dominant-negative (dn) STAT5a that blocks the dimerization of STAT5 and inhibits its nuclear translocation. We found that dn-STAT5a inhibited Involucrin expression in keratinocytes. Given that STAT5 regulates adipogenesis via activating the peroxisome proliferator-activated receptor (PPAR) γ signal, we hypothesized that STAT5a regulated Involucrin expression in the same manner. To test this hypothesis, we examined the expression and transactivation of PPAR γ in a suspension culture of keratinocytes. Suspension culture induced PPAR γ expression and triggered PPAR γ transactivation rapidly and dn-STAT5a downregulated this induction and suppressed PPAR γ transactivation. Furthermore, preincubation with the PPAR γ /retinoid X-receptor inhibitor HX-531 or the introduction of a dn-PPAR γ prevented the activation of Involucrin promoter and inhibited its induction. This report provides early evidence of a major role for STAT5a in the differentiation of keratinocytes, where it contributes to Involucrin expression by activating the PPAR γ signal.
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STAT5a/PPARγ Pathway Regulates Involucrin Expression in Keratinocyte Differentiation
Journal of Investigative Dermatology, 2007Co-Authors: Koji Sayama, Sho Tokumaru, Satoshi Hirakawa, Lujun Yang, Kenshi Yamasaki, Yasushi Hanakawa, Yuji Shirakata, Xiaoling Wang, Mikiko TohyamaAbstract:Signal transducers and activators of transcription (STATs) are critical to growth factor-mediated intracellular signal transduction. We observed the rapid expression and activation of STAT5a during keratinocyte differentiation induced by suspension culture. STAT5a expression preceded that of Involucrin, an important molecule in the terminal differentiation of keratinocytes. To determine whether STAT5a regulated Involucrin expression, we expressed a dominant-negative (dn) STAT5a that blocks the dimerization of STAT5 and inhibits its nuclear translocation. We found that dn-STAT5a inhibited Involucrin expression in keratinocytes. Given that STAT5 regulates adipogenesis via activating the peroxisome proliferator-activated receptor (PPAR) γ signal, we hypothesized that STAT5a regulated Involucrin expression in the same manner. To test this hypothesis, we examined the expression and transactivation of PPAR γ in a suspension culture of keratinocytes. Suspension culture induced PPAR γ expression and triggered PPAR γ transactivation rapidly and dn-STAT5a downregulated this induction and suppressed PPAR γ transactivation. Furthermore, preincubation with the PPAR γ /retinoid X-receptor inhibitor HX-531 or the introduction of a dn-PPAR γ prevented the activation of Involucrin promoter and inhibited its induction. This report provides early evidence of a major role for STAT5a in the differentiation of keratinocytes, where it contributes to Involucrin expression by activating the PPAR γ signal.
Mikiko Tohyama - One of the best experts on this subject based on the ideXlab platform.
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PPARγ is an important transcription factor in 1α, 25-dihydroxyvitamin D3-induced Involucrin expression
Journal of Dermatological Science, 2008Co-Authors: Xiuju Dai, Sho Tokumaru, Satoshi Hirakawa, Lujun Yang, Yasushi Hanakawa, Yuji Shirakata, Koji Sayama, Mikiko Tohyama, Koji HashimotoAbstract:Summary Background 1α,25-Dihydroxyvitamin D3 (1α,25(OH)2D3), the active form of vitamin D, suppresses keratinocyte proliferation, promotes keratinocyte differentiation, and induces Involucrin expression. Peroxisome proliferation-activated receptors (PPARs) are ligand-activated transcription factors. It has been reported that PPARs stimulate keratinocyte differentiation and regulate the expression of differentiation molecules. Objective Keratinocytes treated with 1α,25(OH)2D3 induced PPARγ, which was followed by increased Involucrin expression. In this study, we investigated whether PPARγ is involved in the 1α,25(OH)2D3-induced Involucrin expression in human keratinocytes. Methods Subconfluent keratinocytes were treated with 10−7 M 1α,25(OH)2D3 for the indicated times, and PPAR and Involucrin mRNA expression were determined by real-time RT-PCR. The levels of PPARs, Involucrin, p38, and phospho-p38 proteins were assayed by Western blotting, and the DNA binding activities of PPARγ and AP-1 were investigated by electrophoretic mobility shift assays (EMSA). To examine the role of PPARγ in 1α,25(OH)2D3 responses, recombinant adenovirus carrying a dominant-negative form of PPARγ (Axdn-PPARγ) was constructed and transfected into keratinocytes. The p38 inhibitor SB203580 was added to the cultures to evaluate the involvement of p38 in Involucrin expression. Results 1α,25(OH)2D3 induced PPARγ expression and stimulated PPARγ activity. The introduction of dn-PPARγ inhibited the expression of Involucrin mRNA and protein induced by 1α,25(OH)2D3, and suppressed AP-1 DNA binding activity. 1α,25(OH)2D3 also triggered the phosphorylation of p38, which contributes to Involucrin induction. Moreover, dn-PPARγ prevented the 1α,25(OH)2D3-induced phosphorylation of p38. Conclusions These results suggest that PPARγ regulates Involucrin expression by controlling the AP-1 signal and p38 activation in 1α,25(OH)2D3-induced keratinocyte differentiation.
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stat5a pparγ pathway regulates Involucrin expression in keratinocyte differentiation
Journal of Investigative Dermatology, 2007Co-Authors: Koji Sayama, Sho Tokumaru, Satoshi Hirakawa, Lujun Yang, Kenshi Yamasaki, Yasushi Hanakawa, Yuji Shirakata, Mikiko Tohyama, Xiaoling Wang, Toshimasa YamauchiAbstract:Signal transducers and activators of transcription (STATs) are critical to growth factor-mediated intracellular signal transduction. We observed the rapid expression and activation of STAT5a during keratinocyte differentiation induced by suspension culture. STAT5a expression preceded that of Involucrin, an important molecule in the terminal differentiation of keratinocytes. To determine whether STAT5a regulated Involucrin expression, we expressed a dominant-negative (dn) STAT5a that blocks the dimerization of STAT5 and inhibits its nuclear translocation. We found that dn-STAT5a inhibited Involucrin expression in keratinocytes. Given that STAT5 regulates adipogenesis via activating the peroxisome proliferator-activated receptor (PPAR) γ signal, we hypothesized that STAT5a regulated Involucrin expression in the same manner. To test this hypothesis, we examined the expression and transactivation of PPAR γ in a suspension culture of keratinocytes. Suspension culture induced PPAR γ expression and triggered PPAR γ transactivation rapidly and dn-STAT5a downregulated this induction and suppressed PPAR γ transactivation. Furthermore, preincubation with the PPAR γ /retinoid X-receptor inhibitor HX-531 or the introduction of a dn-PPAR γ prevented the activation of Involucrin promoter and inhibited its induction. This report provides early evidence of a major role for STAT5a in the differentiation of keratinocytes, where it contributes to Involucrin expression by activating the PPAR γ signal.
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STAT5a/PPARγ Pathway Regulates Involucrin Expression in Keratinocyte Differentiation
Journal of Investigative Dermatology, 2007Co-Authors: Koji Sayama, Sho Tokumaru, Satoshi Hirakawa, Lujun Yang, Kenshi Yamasaki, Yasushi Hanakawa, Yuji Shirakata, Xiaoling Wang, Mikiko TohyamaAbstract:Signal transducers and activators of transcription (STATs) are critical to growth factor-mediated intracellular signal transduction. We observed the rapid expression and activation of STAT5a during keratinocyte differentiation induced by suspension culture. STAT5a expression preceded that of Involucrin, an important molecule in the terminal differentiation of keratinocytes. To determine whether STAT5a regulated Involucrin expression, we expressed a dominant-negative (dn) STAT5a that blocks the dimerization of STAT5 and inhibits its nuclear translocation. We found that dn-STAT5a inhibited Involucrin expression in keratinocytes. Given that STAT5 regulates adipogenesis via activating the peroxisome proliferator-activated receptor (PPAR) γ signal, we hypothesized that STAT5a regulated Involucrin expression in the same manner. To test this hypothesis, we examined the expression and transactivation of PPAR γ in a suspension culture of keratinocytes. Suspension culture induced PPAR γ expression and triggered PPAR γ transactivation rapidly and dn-STAT5a downregulated this induction and suppressed PPAR γ transactivation. Furthermore, preincubation with the PPAR γ /retinoid X-receptor inhibitor HX-531 or the introduction of a dn-PPAR γ prevented the activation of Involucrin promoter and inhibited its induction. This report provides early evidence of a major role for STAT5a in the differentiation of keratinocytes, where it contributes to Involucrin expression by activating the PPAR γ signal.
