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Cholestasis induces reversible accumulation of periplakin in mouse liver.

Ito S, Satoh J, Matsubara T, Shah YM, Ahn SH, Anderson CR, Shan W, Peters JM, Gonzalez FJ - BMC Gastroenterol (2013)

Bottom Line: PPL serves as a structural component of the cornified envelope in the skin and interacts with various types of proteins in cultured cells; its level decreases dramatically during tumorigenic progression in human epithelial tissues.In addition, similar accumulation of PPL at cellular boundaries was found in epithelial cells around renal tubules upon ureteral obstruction.Further examination of the roles for PPL may lead to the discovery of a novel mechanism for cellular protection by cytolinkers that is applicable to many tissues and in many contexts.

View Article: PubMed Central - HTML - PubMed

Affiliation: Biofrontier Platform, Graduate School of Medicine, Kyoto University, Yoshida Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan. ito.shinji.3v@kyoto-u.ac.jp

ABSTRACT

Background: Periplakin (PPL) is a rod-shaped cytolinker protein thought to connect cellular adhesion junctional complexes to cytoskeletal filaments. PPL serves as a structural component of the cornified envelope in the skin and interacts with various types of proteins in cultured cells; its level decreases dramatically during tumorigenic progression in human epithelial tissues. Despite these intriguing observations, the physiological roles of PPL, especially in non-cutaneous tissues, are still largely unknown. Because we observed a marked fluctuation of PPL expression in mouse liver in association with the bile acid receptor farnesoid X receptor (FXR) and cholestasis, we sought to characterize the role of PPL in the liver and determine its contributions to the etiology and pathogenesis of cholestasis.

Methods: Time- and context-dependent expression of PPL in various mouse models of hepatic and renal disorders were examined by immunohistochemistry, western blotting, and quantitative real-time polymerase chain reactions.

Results: The hepatic expression of PPL was significantly decreased in Fxr-/- mice. In contrast, the expression was dramatically increased during cholestasis, with massive PPL accumulation observed at the boundaries of hepatocytes in wild-type mice. Interestingly, the hepatic accumulation of PPL resulting from cholestasis was reversible. In addition, similar accumulation of PPL at cellular boundaries was found in epithelial cells around renal tubules upon ureteral obstruction.

Conclusions: PPL may be involved in the temporal accommodation to fluid stasis in different tissues. Further examination of the roles for PPL may lead to the discovery of a novel mechanism for cellular protection by cytolinkers that is applicable to many tissues and in many contexts.

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Immunohistochemical localization of PPL in normal liver. (A) Representative images for the localization of PPL and K19 in normal liver. PPL and K19 were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Scale bars: 100 μm (upper) and 25 μm (lower). (B) PPL and ZO-1 were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Arrowheads indicate PPL expression at ZO-1-negative sites. Scale bars: 100 μm (upper) and 25 μm (lower). (C) MDR and ZO-1 were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Scale bar: 25 μm. (D) PPL and γ-catenin (γ-CTN) were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Scale bar: 25 μm. (E) PPL and K19 were double-stained by red and green fluorescence, respectively. Signals for PPL were absent in cholangiocytes and hepatocytes of Ppl−/− mice. Scale bar: 100 μm. PV, portal vein; BD, bile duct.
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Figure 2: Immunohistochemical localization of PPL in normal liver. (A) Representative images for the localization of PPL and K19 in normal liver. PPL and K19 were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Scale bars: 100 μm (upper) and 25 μm (lower). (B) PPL and ZO-1 were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Arrowheads indicate PPL expression at ZO-1-negative sites. Scale bars: 100 μm (upper) and 25 μm (lower). (C) MDR and ZO-1 were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Scale bar: 25 μm. (D) PPL and γ-catenin (γ-CTN) were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Scale bar: 25 μm. (E) PPL and K19 were double-stained by red and green fluorescence, respectively. Signals for PPL were absent in cholangiocytes and hepatocytes of Ppl−/− mice. Scale bar: 100 μm. PV, portal vein; BD, bile duct.

Mentions: Next, we determined the localization of PPL in the liver of wild-type mice by immunohistochemical analysis. The highest expression of PPL was detected in bile duct epithelial cells co-expressing K19, a cholangiocyte marker (Figure 2A). PPL was also detected at the boundaries of hepatocytes and overlapped with the tight junction protein ZO-1, a marker for the bile canalicular membrane (Figure 2B). Faint expression was also noted at cellular borders lacking ZO-1 staining (Figure 2B, arrowheads). In contrast to PPL, the bile canalicular MDR (P-glycoproteins) were almost exclusively found in areas surrounded by ZO-1 (Figure 2C). Thus, PPL localizes not only near the bile canaliculi but also near other cellular boundaries of hepatocytes. The expression of PPL partially overlapped with that of the desmosomal protein γ-CTN (Figure 2D). Similar partially overlapping expression of PPL with desmosomal protein has also been reported in cultured keratinocytes [13]. Importantly, PPL expression was undetectable by immunohistochemical analysis in Ppl−/− mice, thus demonstrating antibody specificity (Figure 2E). In line with these results, human PPL mRNA expression was also found to be high in a cholangiocyte-derived cell line (HuH7), considerably lower in a hepatocyte-derived cell line (HepG2), and almost undetectable in a hepatic stellate cell-derived cell line (LX-2) (data not shown).


Cholestasis induces reversible accumulation of periplakin in mouse liver.

Ito S, Satoh J, Matsubara T, Shah YM, Ahn SH, Anderson CR, Shan W, Peters JM, Gonzalez FJ - BMC Gastroenterol (2013)

Immunohistochemical localization of PPL in normal liver. (A) Representative images for the localization of PPL and K19 in normal liver. PPL and K19 were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Scale bars: 100 μm (upper) and 25 μm (lower). (B) PPL and ZO-1 were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Arrowheads indicate PPL expression at ZO-1-negative sites. Scale bars: 100 μm (upper) and 25 μm (lower). (C) MDR and ZO-1 were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Scale bar: 25 μm. (D) PPL and γ-catenin (γ-CTN) were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Scale bar: 25 μm. (E) PPL and K19 were double-stained by red and green fluorescence, respectively. Signals for PPL were absent in cholangiocytes and hepatocytes of Ppl−/− mice. Scale bar: 100 μm. PV, portal vein; BD, bile duct.
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Figure 2: Immunohistochemical localization of PPL in normal liver. (A) Representative images for the localization of PPL and K19 in normal liver. PPL and K19 were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Scale bars: 100 μm (upper) and 25 μm (lower). (B) PPL and ZO-1 were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Arrowheads indicate PPL expression at ZO-1-negative sites. Scale bars: 100 μm (upper) and 25 μm (lower). (C) MDR and ZO-1 were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Scale bar: 25 μm. (D) PPL and γ-catenin (γ-CTN) were double-stained by red and green fluorescence, respectively. Merged images are shown on the right. Scale bar: 25 μm. (E) PPL and K19 were double-stained by red and green fluorescence, respectively. Signals for PPL were absent in cholangiocytes and hepatocytes of Ppl−/− mice. Scale bar: 100 μm. PV, portal vein; BD, bile duct.
Mentions: Next, we determined the localization of PPL in the liver of wild-type mice by immunohistochemical analysis. The highest expression of PPL was detected in bile duct epithelial cells co-expressing K19, a cholangiocyte marker (Figure 2A). PPL was also detected at the boundaries of hepatocytes and overlapped with the tight junction protein ZO-1, a marker for the bile canalicular membrane (Figure 2B). Faint expression was also noted at cellular borders lacking ZO-1 staining (Figure 2B, arrowheads). In contrast to PPL, the bile canalicular MDR (P-glycoproteins) were almost exclusively found in areas surrounded by ZO-1 (Figure 2C). Thus, PPL localizes not only near the bile canaliculi but also near other cellular boundaries of hepatocytes. The expression of PPL partially overlapped with that of the desmosomal protein γ-CTN (Figure 2D). Similar partially overlapping expression of PPL with desmosomal protein has also been reported in cultured keratinocytes [13]. Importantly, PPL expression was undetectable by immunohistochemical analysis in Ppl−/− mice, thus demonstrating antibody specificity (Figure 2E). In line with these results, human PPL mRNA expression was also found to be high in a cholangiocyte-derived cell line (HuH7), considerably lower in a hepatocyte-derived cell line (HepG2), and almost undetectable in a hepatic stellate cell-derived cell line (LX-2) (data not shown).

Bottom Line: PPL serves as a structural component of the cornified envelope in the skin and interacts with various types of proteins in cultured cells; its level decreases dramatically during tumorigenic progression in human epithelial tissues.In addition, similar accumulation of PPL at cellular boundaries was found in epithelial cells around renal tubules upon ureteral obstruction.Further examination of the roles for PPL may lead to the discovery of a novel mechanism for cellular protection by cytolinkers that is applicable to many tissues and in many contexts.

View Article: PubMed Central - HTML - PubMed

Affiliation: Biofrontier Platform, Graduate School of Medicine, Kyoto University, Yoshida Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan. ito.shinji.3v@kyoto-u.ac.jp

ABSTRACT

Background: Periplakin (PPL) is a rod-shaped cytolinker protein thought to connect cellular adhesion junctional complexes to cytoskeletal filaments. PPL serves as a structural component of the cornified envelope in the skin and interacts with various types of proteins in cultured cells; its level decreases dramatically during tumorigenic progression in human epithelial tissues. Despite these intriguing observations, the physiological roles of PPL, especially in non-cutaneous tissues, are still largely unknown. Because we observed a marked fluctuation of PPL expression in mouse liver in association with the bile acid receptor farnesoid X receptor (FXR) and cholestasis, we sought to characterize the role of PPL in the liver and determine its contributions to the etiology and pathogenesis of cholestasis.

Methods: Time- and context-dependent expression of PPL in various mouse models of hepatic and renal disorders were examined by immunohistochemistry, western blotting, and quantitative real-time polymerase chain reactions.

Results: The hepatic expression of PPL was significantly decreased in Fxr-/- mice. In contrast, the expression was dramatically increased during cholestasis, with massive PPL accumulation observed at the boundaries of hepatocytes in wild-type mice. Interestingly, the hepatic accumulation of PPL resulting from cholestasis was reversible. In addition, similar accumulation of PPL at cellular boundaries was found in epithelial cells around renal tubules upon ureteral obstruction.

Conclusions: PPL may be involved in the temporal accommodation to fluid stasis in different tissues. Further examination of the roles for PPL may lead to the discovery of a novel mechanism for cellular protection by cytolinkers that is applicable to many tissues and in many contexts.

Show MeSH
Related in: MedlinePlus