Search

Extracellular matrix (ECM) proteins are synthesized in the endoplasmic reticulum (ER), transported to the extracellular milieu through the secretory pathway, and assembled into an extracellular architecture. A previous study of ours showed that periostin, a secretory protein, interacts with fibronectin and is involved in ECM remodeling. Here we show that periostin played a role in fibronectin secretion from the ER. Co-immunoprecipitation and in situ proximity ligation assays revealed an interaction between periostin and fibronectin in the ER. Although accumulation of fibronectin was detected in the ER of fibroblastic C3H10T1/2 cells, forced expression of periostin in those cells decreased the accumulation of fibronectin in the ER, suggesting that periostin promoted the secretion of fibronectin. A substitution mutant of tryptophan at the position 65 to alanine in the EMI domain of periostin, which caused periostin to lose its ability to interact with fibronectin, did not decrease the accumulation. Furthermore, targeted disruption of periostin in mice caused the non-fibrillar and ectopic deposition of fibronectin in the periodontal ligament. Thus, these results demonstrate a subcellular role of periostin in promotion of fibronectin secretion from the ER. [ABSTRACT FROM AUTHOR]

Background: Matricellular proteins, including periostin, modulate cell-matrix interactions and cell functions by acting outside of cells. Methods and Findings: In this study, however, we reported that periostin physically associates with the Notch1 precursor at its EGF repeats in the inside of cells. Moreover, by using the periodontal ligament of molar from periostin-deficient adult mice (Pn-/- molar PDL), which is a constitutively mechanically stressed tissue, we found that periostin maintained the site-1 cleaved 120-kDa transmembrane domain of Notch1 (N1™) level without regulating Notch1 mRNA expression. N1™ maintenance in vitro was also observed under such a stress condition as heat and H2O2 treatment in periostin overexpressed cells. Furthermore, we found that the expression of a downstream effector of Notch signaling, Bcl-xL was decreased in the Pn-/- molar PDL, and in the molar movement, cell death was enhanced in the pressure side of Pn-/- molar PDL. Conclusion: These results suggest the possibility that periostin inhibits cell death through up-regulation of Bcl-xL expression by maintaining the Notch1 protein level under the stress condition, which is caused by its physical association with the Notch1 precursor. [ABSTRACT FROM AUTHOR]

Periostin is a matricellular protein participating in the tissue remodelling of damaged cardiac tissue after acute myocardial infarction and of the periodontal ligament in mice. However, further studies on the periostin protein have been limited by the intrinsic difficulty of purifying this protein produced in Escherichia coli due to its insolubility. Here, we demonstrate the expression of recombinant periostin protein with high solubility and monodispersity in E. coli. Periostin is composed of an amino-terminal EMI domain, a tandem repeat of 4 fas1 domains (RD1-4), and a carboxyl-terminal region (CTR). We expressed the RD4-CTR region tagged with GST at amino-terminal and 6× Histidine at carboxyl-terminal end in E. coli. The recombinant protein was purified by using GSH-Sepharose and nickel chelation affinity chromatography, followed by gel filtration chromatography. The RD4-CTR protein exhibited high solubility and monodispersity. On average, 9.1 mg of purified RD4-CTR was routinely obtained from 1 L of culture media. Furthermore, the RD4-CTR was biochemically active, because it bound to the RD1-4, the same as intact periostin protein that had been purified from mammalian cells. Our results should enable us to produce the periostin recombinant protein in large quantities and facilitate future studies on functional and structural analyses of periostin. [ABSTRACT FROM PUBLISHER]

Abstract: A characteristic tooth of rodents, the incisor continuously grows throughout life by the constant formation of dentin and enamel. Continuous eruption of the incisor is accompanied with formation of shear zone, in which the periodontal ligament is remodeled. Although the shear zone plays a role in the remodeling, its molecular biological aspect is barely understood. Here, we show that periostin is essential for formation of the shear zone. Periostin −/− mice showed an eruption disturbance of incisors. Histological observation revealed that deletion of periostin led to disappearance of the shear zone. Electron microscopy revealed that the disappearance of the shear zone resulted from a failure in digestion of collagen fibers in the periostin −/− mice. Furthermore, immunohistochemical analysis using anti-periostin antibodies demonstrated the restricted localization of periostin protein in the shear zone. Periostin is an extracellular matrix protein, and immunoelectron microscopy showed a close association of periostin with collagen fibrils in vivo. These results suggest that periostin functions in the remodeling of collagen matrix in the shear zone. [Copyright &y& Elsevier]