Search

Extracellular matrix (ECM) has a marked influence on adipose tissue development. Adipose tissue formation is initiated with proliferation of preadipocytes and migration before undergoing further differentiation into mature adipocytes. Previous studies showed that collagen I (col I) provides a good substratum for 3T3‐L1 preadipocytes to grow and migrate. However, it remains unclear whether and how col I regulates adipogenic differentiation of preadipocytes. This study reports that lipid accumulation, representing in vitro adipogenesis of the 3T3‐L1 preadipocytes or the mouse primary adipocyte precursor cells derived from subcutaneous adipose tissue in the inguinal region is inhibited by the culture on col I, owing to downregulation of adipogenic factors. Previous study shows that col I enhances 3T3‐L1 cell migration via stimulating the nuclear translocation of yes‐associated protein (YAP). In this study, we report that downregulation of YAP is associated with in vitro adipogenesis of preadipocytes as well as with in vivo adipose tissue of high‐fat diet fed mice. Increased expression of YAP in the cells cultured on col I‐coated dishes is correlated with repression of adipogenic differentiation processes. The inactivation of YAP using YAP inhibitor, verteporfin, or YAP small‐interfering RNA enhanced adipogenic differentiation and reversed the inhibitory effect of col I. Activation of YAP either by the transfection of YAP plasmid or the silence of large tumor suppressor 1 (LATS1), an inhibitory kinase of YAP, inhibited adipogenic differentiation. The results indicate that col I inhibits adipogenic differentiation via YAP activation in vitro. [ABSTRACT FROM AUTHOR]

The single-crystal structure of the collagen-like peptide (Pro-Pro-Gly)4-Hyp-Asp-Gly-(Pro-Pro-Gly)4, was analyzed at 1.02 Å resolution. The overall average helical twist (θ = 49.6°) suggests that this peptide adopts a 7/2 triple-helical structure and that its conformation is very similar to that of (Gly-Pro-Hyp)9, which has the typical repeating sequence in collagen. High-resolution studies on other collagen-like peptides have shown that imino acid-rich sequences preferentially adopt a 7/2 triple-helical structure (θ = 51.4°), whereas imino acid-lean sequences adopt relaxed conformations (θ < 51.4°). The guest Gly-Hyp-Asp sequence in the present peptide, however, has a large helical twist (θ = 61.1°), whereas that of the host Pro-Pro-Gly sequence is small (θ = 46.7°), indicating that the relationship between the helical conformation and the amino acid sequence of such peptides is complex. In the present structure, a strong intermolecular hydrogen bond between two Asp residues on the A and B strands might induce the large helical twist of the guest sequence; this is compensated by a reduced helical twist in the host, so that an overall 7/2-helical symmetry is maintained. The Asp residue in the C strand might interact electrostatically with the N-terminus of an adjacent molecule, causing axial displacement, reminiscent of the D-staggered structure in fibrous collagens. © 2013 Wiley Periodicals, Inc. Biopolymers 99: 436-447, 2013. [ABSTRACT FROM AUTHOR]

Collagens have long been believed to adopt a triple-stranded molecular structure with a 10/3 symmetry (ten triplet units in three turns) and an axial repeat of 29 Å. This belief even persisted after an alternative structure with a 7/2 symmetry (seven triplet units in two turns) with an axial repeat of 20 Å had been proposed. The uncertainty regarding the helical symmetry of collagens is attributed to inadequate X-ray fiber diffraction data. Therefore, for better understanding of the collagen helix, single-crystal analyses of peptides with simplified characteristic amino acid sequences and similar compositions to collagens have long been awaited. Here we report the crystal structure of (Gly-Pro-Hyp)9 peptide at a resolution of 1.45 Å. The repeating unit of this peptide, Gly-Pro-Hyp, is the most typical sequence present in collagens, and it has been used as a basic repeating unit in fiber diffraction analyses of collagen. The (Gly-Pro-Hyp)9 peptide adopts a triple-stranded structure with an average helical symmetry close to the ideal 7/2 helical model for collagen. This observation strongly suggests that the average molecular structure of collagen is not the accepted Rich and Crick 10/3 helical model but is a 7/2 helical conformation. © 2012 Wiley Periodicals, Inc. Biopolymers 97: 607-616, 2012. [ABSTRACT FROM AUTHOR]

The single-crystal structures of three collagen-like host-guest peptides, (Pro-Pro-Gly)-Hyp-Yaa-Gly-(Pro-Pro-Gly) [Yaa = Thr, Val, Ser; Hyp = (4 R)-4-hydroxyproline] were analyzed at atomic resolution. These peptides adopted a 7/2-helical structure similar to that of the (Pro-Pro-Gly) peptide. The stability of these triple helices showed a similar tendency to that observed in Ac-(Gly-Hyp-Yaa)-NH (Yaa = Thr, Val, Ser) peptides. On the basis of their detailed structures, the differences in the triple-helical stabilities of the peptides containing a Hyp-Thr-Gly, Hyp-Val-Gly, or Hyp-Ser-Gly sequence were explained in terms of van der Waals interactions and dipole-dipole interaction between the Hyp residue in the X position and the Yaa residue in the Y position involved in the Hyp(X):Yaa(Y) stacking pair. This idea also explains the inability of Ac-(Gly-Hyp-alloThr)-NH and Ac-(Gly-Hyp-Ala)-NH peptides to form triple helices. In the Hyp(X):Thr(Y), Hyp(X):Val(Y), and Hyp(X):Ser(Y) stacking pairs, the proline ring of the Hyp residues adopts an up-puckering conformation, in agreement with the residual preference of Hyp, but in disagreement with the positional preference of X in the Gly-Xaa-Yaa sequence. © 2011 Wiley Periodicals, Inc. Biopolymers 95: 628-640, 2011. [ABSTRACT FROM AUTHOR]

Two crystal modifications of a collagen model peptide, (Pro-Pro-Gly)4-Hyp-Hyp-Gly-(Pro-Pro-Gly)4 [where Hyp is (4R,2S)-L-hydroxyproline], showed very similar unit-cell parameters and belonged to the same space group P21. Both crystals exhibited pseudo-merohedral twinning. The main difference was in their molecular-packing arrangements. One modification showed pseudo-hexagonal packing, while the other showed pseudo-tetragonal packing. Despite their different packing arrangements, no significant differences were observed in the hydration states of these modifications. The peptide in the pseudo-tetragonal crystal showed a cyclic fluctuation of helical twists with a period of 20 Å, while that in the pseudo-hexagonal crystal did not. In these modifications, the puckering conformations of four of the 12 Hyp residues at the X position of the Hyp(X)-Hyp(Y)-Gly sequence were in the opposite conformations to the previous hypothesis that Hyp(X) residues involved in Hyp(X):Hyp(Y) and Hyp(X): Pro(Y) stacking pairs prefer up-puckering and down-puckering conformations, respectively. Detailed investigation of the molecular interactions between Hyp(X) and adjacent molecules revealed that these opposite conformations appeared because the puckering conformation, which follows the hypothesis, is subject to steric hindrance from the adjacent molecule. [ABSTRACT FROM AUTHOR]

In order to evaluate the role of 3( S)-hydroxyproline [3( S)-Hyp] in the triple-helical structure, we produced a series of model peptides with nine tripeptide units including 0–9 3( S)-hydroxyproline residues. The sequences are H-(Gly-Pro-4( R)Hyp) l-(Gly-3( S)Hyp-4( R)Hyp) m-(Gly-Pro-4( R)Hyp) n-OH, where ( l, m, n) = (9, 0, 0), (4, 1, 4), (3, 2, 4), (3, 3, 3), (1, 7, 1) and (0, 9, 0). All peptides showed triple-helical CD spectra at room temperature and thermal transition curves. Sedimentation equilibrium analysis showed that peptide H-(Gly-3( S)Hyp-4( R)Hyp)9-OH is a trimer. Differential scanning calorimetry showed that replacement of Pro residues with 3( S)Hyp residues decreased the transition enthalpy, and the transition temperature increases by 4.5 °C from 52.0 °C for the peptide with no 3( S)Hyp residues to 56.5 °C for the peptide with nine 3( S)Hyp residues. The refolding kinetics of peptides H-(Gly-3( S)Hyp-4( R)Hyp)9-OH, H-(Gly-Pro-4( R)Hyp)9-OH and H-(Gly-4( R)Hyp-4( R)Hyp)9-OH were compared, and the apparent reaction orders of refolding at 10 °C were n = 1.5, 1.3 and 1.2, respectively. Replacement of Pro with 3( S)Hyp or 4( R)Hyp has little effect on the refolding kinetics. This result suggests that the refolding kinetics of collagen model peptides are influenced mainly by the residue in the Yaa position of the -Gly-Xaa-Yaa- repeated sequence. The experiments indicate that replacement of a Pro residue by a 3( S)Hyp residue in the Xaa position of the -Gly-Xaa-4( R)Hyp- repeat of collagen model peptides increases the stability, mainly due to entropic factors. [ABSTRACT FROM AUTHOR]

In this paper, the authors propose a method of systematically generating 3-colorable (3COL) graph instances for which a great deal of time and effort are required to obtain a solution (or to determine solvability). This method, which differs from the conventional approach of selecting hard instances from among randomly generated instances, aims to reliably generate hard problems by repeatedly embedding 3COL minimal unsolvable structures in the initial graph. The generated instances conform to various conditions of problems for which the solution searches that had been identified conventionally are extremely difficult. Also, the authors use several solution search algorithms to experimentally verify that the required effort is an exponential order of the number of vertices. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 90(12): 27–35, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20359 [ABSTRACT FROM AUTHOR]

Background: There is increasing concern in Japan over infants with atopic dermatitis (AD) who present with severe systemic complications, such as hypoproteinemia, electrolyte disturbances, and delayed growth and development. They are often associated with extremely increased numbers of circulating eosinophils. However, the clinical significance of eosinophil expansion has not been thoroughly investigated.Methods: This study attempted to determine the significance of eosinophilia and eosinophil activation in infant cases of AD by comparing multiple clinical parameters, indexes of eosinophil activation, and levels of serum cytokines. CD69 expression was determined by flow cytometry. The clinical severity of AD was graded by the severity SCORing of atopic dermatitis (SCORAD) method. Patients were classified into two groups, with and without CD69 on eosinophils. Nuclear lobes were evaluated under a microscopy. Serum levels of eosinophil-derived neurotoxin (EDN), interleukin (IL)-12, IL-18, IL-4, IL-5 and interferon (IFN)-γ were determined by enzyme-linked immunosorbent assay.Results: Patients with CD69-positive eosinophils had significantly higher numbers of eosinophils and platelets, total IgE, and eosinophil nuclear lobes. They also showed growth failure, developmental delay, low serum albumin, and electrolyte disturbances. EDN and IL-18 levels were significantly increased in this group, but the levels of IL-4, IL-5 and IL-12 were not significantly different between the two groups. IFN-γ was not detectable in all patients with AD. Surface expression of CD69 indicates intense systemic allergic inflammation induced in severe cases of AD.Conclusions: Evaluation of eosinophil activation and early therapeutic intervention is mandatory for the treatment of severe AD during infancy. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Microfibrillar Structure of Type 1 Collagen in Situ," published in the "Proceedings of the National Academy of Sciences."

Two crystal modifications of a collagen model peptide, (Pro-Pro-Gly)(4)-Hyp-Hyp-Gly-(Pro-Pro-Gly)(4) [where Hyp is (4R,2S)-L-hydroxyproline], showed very similar unit-cell parameters and belonged to the same space group P2(1). Both crystals exhibited pseudo-merohedral twinning. The main difference was in their molecular-packing arrangements. One modification showed pseudo-hexagonal packing, while the other showed pseudo-tetragonal packing. Despite their different packing arrangements, no significant differences were observed in the hydration states of these modifications. The peptide in the pseudo-tetragonal crystal showed a cyclic fluctuation of helical twists with a period of 20 A, while that in the pseudo-hexagonal crystal did not. In these modifications, the puckering conformations of four of the 12 Hyp residues at the X position of the Hyp(X)-Hyp(Y)-Gly sequence were in the opposite conformations to the previous hypothesis that Hyp(X) residues involved in Hyp(X):Hyp(Y) and Hyp(X):Pro(Y) stacking pairs prefer up-puckering and down-puckering conformations, respectively. Detailed investigation of the molecular interactions between Hyp(X) and adjacent molecules revealed that these opposite conformations appeared because the puckering conformation, which follows the hypothesis, is subject to steric hindrance from the adjacent molecule.