Dyrk1A (dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 1A) is a serine/ threonine kinase essential for brain development and function, and its excessive activity is considered a pathogenic factor in Down syndrome. The development of potent, selective inhibitors of Dyrk1A would help to elucidate the molecular mechanisms of normal and diseased brains, and may provide a new lead compound for molecular-targeted drug discovery. Here, we report a novel Dyrk1A inhibitor, InDY, a benzothiazole derivative showing a potent ATPcompetitive inhibitory effect with IC 50 and K i values of 0.24 and 0.18 µm, respectively. X-ray crystallography of the Dyrk1A/InDY complex revealed the binding of InDY in the ATP pocket of the enzyme. InDY effectively reversed the aberrant tau-phosphorylation and rescued the repressed nFAT (nuclear factor of activated T cell) signalling induced by Dyrk1A overexpression. Importantly, proInDY, a prodrug of InDY, effectively recovered Xenopus embryos from head malformation induced by Dyrk1A overexpression, resulting in normally developed embryos and demonstrating the utility of proInDY in vivo.

Extracellular matrix (ECM) underlies a complicated multicellular architecture that is subjected to significant forces from mechanical environment. Although various components of the ECM have been enumerated, mechanisms that evolve the sophisticated ECM architecture remain to be addressed. Here we show that periostin, a matricellular protein, promotes incorporation of tenascin-C into the ECM and organizes a meshwork architecture of the ECM. We found that both periostin null mice and tenascin-C null mice exhibited a similar phenotype, confined tibial periostitis, which possibly corresponds to medial tibial stress syndrome in human sports injuries. Periostin possessed adjacent domains that bind to tenascin-C and the other ECM protein: fibronectin and type I collagen, respectively. These adjacent domains functioned as a bridge between tenascin-C and the ECM, which increased deposition of tenascin-C on the ECM. The deposition of hexabrachions of tenascin-C may stabilize bifurcations of the ECM fibrils, which is integrated into the extracellular meshwork architecture. This study suggests a role for periostin in adaptation of the ECM architecture in the mechanical environment.

Acute myocardial infarction (AMI) is a common and lethal heart disease, and the recruitment of fibroblastic cells to the infarct region is essential for the cardiac healing process. Although stiffness of the extracellular matrix in the infarct myocardium is associated with cardiac healing, the molecular mechanism of cardiac healing is not fully understood. We show that periostin, which is a matricellular protein, is important for the cardiac healing process after AMI. The expression of periostin protein was abundant in the infarct border of human and mouse hearts with AMI. We generated periostin −/− mice and found no morphologically abnormal cardiomyocyte phenotypes; however, after AMI, cardiac healing was impaired in these mice, resulting in cardiac rupture as a consequence of reduced myocardial stiffness caused by a reduced number of α smooth muscle actin–positive cells, impaired collagen fibril formation, and decreased phosphorylation of FAK. These phenotypes were rescued by gene transfer of a spliced form of periostin. Moreover, the inhibition of FAK or αv-integrin, which blocked the periostin-promoted cell migration, revealed that αv-integrin, FAK, and Akt are involved in periostin signaling. Our novel findings show the effects of periostin on recruitment of activated fibroblasts through FAK-integrin signaling and on their collagen fibril formation specific to healing after AMI.

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Intra-and intermolecular covalent cross-linking between collagen fibrils, catalyzed by lysyl oxidase (LOX), determines the mechanical properties of connective tissues; however, mechanisms that regulate the collagen cross-linking according to tissue specificity are not well understood. Here we show that periostin, a secretory protein in the dense connective tissues, promotes the activation of LOX. Previous studies showed that periostin null mice exhibit reduced collagen cross-linking in their femurs, periosteum, infarcted myocardium, and tendons. Presently, we showed that active LOX protein, formed by cleavage of its propeptide by bone morphogenetic protein-1 (BMP-1), was decreased in calvarial osteoblast cells derived from periostin null mice. Overexpression of periostin promoted the proteolytic cleavage of the propeptide, which increased the amount of active LOX protein. The results of co-immunoprecipitation and solid phase binding assays revealed that periostin interacted with BMP-1. Furthermore, this interaction probably resulted in enhanced deposition of BMP-1 on the extracellular matrix, suggesting that this enhanced deposition would lead to cleavage of the propeptide of LOX. Thus, we demonstrated that periostin supported BMP-1-mediated proteolytic activation of LOX on the extracellular matrix, which promoted collagen cross-linking.Collagen fibrils underlie the mechanical strength of connective tissues, such as bone, tendon, and skin. Post-translational modifications of collagen fibrils are important for both structural and mechanical properties. Collagen fibrillogenesis consists of multiple processes (1). Synthesized pro-collagen chains in the endoplasmic reticulum are folded into the triple helix structure and transported into the Golgi. In the Golgi, procollagens are processed by ADAMTS (pro-collagen N-proteinase) and tolloid (pro-collagen C-proteinase) family enzymes and secreted into the extracellular milieu. Collagen assembles into fibrils, which are then stabilized by the formation of intraand intermolecular cross-linking that is catalyzed by the enzyme lysyl oxidase (LOX).2 The strength of connective tissues is determined by the amount of total collagen cross-linking, as well as by the total collagen content (2-4). The crucial role of collagen cross-linking in connective tissues has been demonstrated in terms of some genetically inherited diseases: Ehlers-Danlos syndrome, homocystinuria, Menkes disease, and occipital horn syndrome. These diseases are attributed to reduced LOX activity, followed by diminished collagen crosslinking, resulting in connective tissue dysfunctions (5-7).LOX catalyzes the oxidative deamination of peptidyl lysine residues in collagen molecules to ␣-aminoadipic-␦-semialdehyde. Spontaneous condensation reactions of the resultant aldehydes lead to the formation of covalent cross-linking in fibrillar collagens (8). This amine oxidase activity of LOX is regulated by proteolytic cleavage of the LOX propeptide. LOX is synthesized as an inactive precursor, pro-LOX, and then activate...