Interaction of procollagen I and other collagens with colligin

Molecular Characterization of Hsp47 in Grass Carp (Ctenopharyngodon idella) and Its Correlation with Type I Collagen in Response to Fish Aerobic Exercise

Heat shock protein 47 (Hsp47) is a collagen-specific molecular chaperone that is indispensable for molecular maturation of collagen. In this study, hsp47 and hsp47-like cDNAs were cloned and characterized in grass carp (Ctenopharyngodon idella). The cDNAs were 1212 and 1218 base pairs long, respectively, and included an open reading frame encoding 403 and 405 amino acids. The molecular phylogeny based on the deduced amino acid sequences indicated that the correct sequences of the hsp47 and hsp47-like cDNA were obtained and the deduced proteins clustered distinctly into teleost clades. Primary structure analysis and characterization of Hsp47 and Hsp47-like shared the basic structure and biofunctions of Hsp47 in vertebrates. The spatial pattern of gene expression revealed that hsp47 and hsp47-like were relatively ubiquitous in different tissues and highly expressed in heart and skin. The expression levels of hsp47 and hsp47-like and type I collagen mRNAs varied similarly in different tissues. Type I collagen content increased significantly with the increase of water velocity in the muscle of grass carp in response to aerobic exercise. Among the gene expression changes of hsp47, hsp47-like, col1a1 and col1a2 in muscle that occurred in response to aerobic exercise, the change of type I collagen was most strongly correlated with hsp47 expression. Additionally, col1a1 showed the highest correlation with hsp47-like and col1a2 showed the highest correlation with hsp47. These findings suggest that grass carp Hsp47 and Hsp47-like are closely related to type I collagen synthesis. This study firstly suggests fish aerobic exercise can improve type I collagen content and Hsp47 gene expression in muscle of grass carp.

Immunohistochemical investigation of wound healing in response to fractional photothermolysis

Despite growing clinical evidence of ablative fractional photothermolysis (AFP), little is known about the spatiotemporal molecular changes within the targeted compartments. Six subjects received three different single AFP treatments using a scanned 250 mum CO(2)-laser beam. Spatiotemporal changes of skin regeneration were estimated by immunohistochemical investigation (HSP70, HSP72, HSP47, TGFbeta, procollagen III, CD3, CD20, and CD68) in skin samples 1 h, 3 days, and 14 days postintervention. The remodeling was uniformly started by regrowth of the epidermal compartment followed by partial to complete replacement of the microscopic ablation zones (MAZ) by newly synthesized condensed procollagen III. From day 3 to 14, the number of macrophages as well as giant cells surrounding the MAZ increased. TGFbeta expression was highest 1 h to 3 days following AFP. HSP70 and HSP72 expressions were highest 3-14 days postintervention in the spinocellular layer leading to an upregulation of HSP47. AFP performed by a scanned CO(2)-laser results in an early epidermal remodeling, which is followed by a dermal remodeling leading to a replacement of the MAZ with newly synthesized (pro)-collagen. During this, an inflammatory infiltrate with CD3(+) and CD20(+) cells surrounds the MAZ. The count of macrophages and giant cells involved in the replacement of the necrotic zones seems to be crucial for wound healing.

Procollagen triple helix assembly: an unconventional chaperone-assisted folding paradigm

Fibers composed of type I collagen triple helices form the organic scaffold of bone and many other tissues, yet the energetically preferred conformation of type I collagen at body temperature is a random coil. In fibers, the triple helix is stabilized by neighbors, but how does it fold? The observations reported here reveal surprising features that may represent a new paradigm for folding of marginally stable proteins. We find that human procollagen triple helix spontaneously folds into its native conformation at 30-34 degrees C but not at higher temperatures, even in an environment emulating Endoplasmic Reticulum (ER). ER-like molecular crowding by nonspecific proteins does not affect triple helix folding or aggregation of unfolded chains. Common ER chaperones may prevent aggregation and misfolding of procollagen C-propeptide in their traditional role of binding unfolded polypeptide chains. However, such binding only further destabilizes the triple helix. We argue that folding of the triple helix requires stabilization by preferential binding of chaperones to its folded, native conformation. Based on the triple helix folding temperature measured here and published binding constants, we deduce that HSP47 is likely to do just that. It takes over 20 HSP47 molecules to stabilize a single triple helix at body temperature. The required 50-200 microM concentration of free HSP47 is not unusual for heat-shock chaperones in ER, but it is 100 times higher than used in reported in vitro experiments, which did not reveal such stabilization.

Mapping Hsp47 binding site(s) using CNBr peptides derived from type I and type II collagen

As a crucial molecular chaperone in collagen biosynthesis, Hsp47 interacts with the nascent form as well as the mature triple-helical form of procollagen. The location(s) of Hsp47 binding sites on the collagen molecule are, as yet, unknown. We have examined the substrate specificity of Hsp47 in vitro using well-characterized CNBr peptide fragments of type I and type II collagen along with radiolabeled, recombinant Hsp47. Interaction of these peptides with Hsp47 bound to collagen-coated microtiter wells showed several binding sites for Hsp47 along the length of the alpha1 and alpha2 chains of type I collagen and the alpha1 chain of type II collagen, with the N-terminal regions showing the strongest affinities. The latter observation was also supported by the results of a ligand-blot assay. Except for two peptides in the alpha2(I) chain, peptides that showed substantial binding to Hsp47 did so in their triple-helical and not random-coil form. Unlike earlier studies that used peptide models for collagen, the results obtained here on fragments of type I and type II collagen identify, for the first time, binding of Hsp47 to specific regions of the collagen molecule. They also point to additional structural requirements for Hsp47 binding besides the known preference for third-position Arg residues and the triple-helical conformation.

Evidence for a direct interaction between the tumor suppressor serpin, maspin, and types I and III collagen

Maspin (mammary serine protease inhibitor) was originally identified as a tumor suppressor protein in human breast epithelial cells and is a member of the serine proteases inhibitor (serpin) superfamily. It inhibits tumor cell motility and angiogenesis, and although predominantly cytoplasmic, it is also localized to the cell surface. In this study we have investigated the use of the yeast two-hybrid interaction trap to identify novel maspin targets. A target human fibroblast cDNA library was screened, and the alpha-2 chain of type I collagen was identified as a potential interactant. Binding studies with isolated proteins showed interaction between recombinant maspin and types I and III collagen but not other collagen subtypes, a profile strikingly similar to mouse pigment epithelium-derived factor (caspin), which is similarly down-regulated in murine adenocarcinoma tumors and is a potent inhibitor of angiogenesis. Kinetic analysis using an IAsys resonant mirror biosensor determined the dissociation constant of maspin for collagen type I to be 0.63 microm. Further two-hybrid interactions with maspin truncation constructs suggest that collagen binding is localized to amino acids 84-112 of maspin, which aligns with the collagen-binding region of colligin. A direct interaction between exogenous or cell surface maspin and extracellular matrix collagen may contribute to a cell adhesion role in the prevention of tumor cell migration and angiogenesis.

A method for expression and purification of soluble, active Hsp47, a collagen-specific molecular chaperone

Hsp47 is regarded as a collagen-specific chaperone with several suggested roles in collagen biosynthesis under normal and disease conditions. We describe here a procedure for the expression and purification of Hsp47 in Escherichia coli using the IMPACT expression system (New England Biolabs) where the guest gene is fused to the adduct, intein, with a chitin-binding domain. Use of this system resulted in relatively high levels of soluble Hsp47 compared to other available protocols, especially when the bacterial cells were induced at 14 degrees C instead of 37 degrees C. The cell lysate was passed through a chitin-Sepharose affinity column and Hsp47 was cleaved from intein using beta-mercaptoethanol. Minor degradation products were subsequently removed using a hydroxylapatite column to yield milligram amounts of pure and active protein suitable for structural studies. Gel electrophoretic analysis of the purified protein indicated the presence of a small proportion of trimeric species when non-reducing conditions were used. The ability to form a trimer may be important for its role as a chaperone. The IMPACT system allows for radiolabelling of purified Hsp47 with (35)S for use in binding experiments. Illustrative data on collagen binding by (35)S-Hsp47 are shown.

Changes in extracellular matrix and in transforming growth factor beta isoforms after coronary artery ligation in rats

Extensive myocardial remodeling occurs after transmural myocardial infarction (MI). The infarcted myocardium is being replaced by scar tissue after gradual resorption of the necrotic tissue. The remodeling process involves both synthesis and degradation of collagens as major components of the extracellular matrix (ECM). In the present study we have analyzed the time-dependent changes of the processes related to this fibrosis in the infarct area and in the non-infarcted left ventricle (LV) six hours to 82 days after occlusion of the left anterior descending coronary artery (LAD) in rats. We also examined whether changes occurred in the expression pattern of the transforming growth factor (TGF) beta isoforms, since this cytokine is known as powerful inductor of fibrosis. Elevation in colligin expression preceded the pronounced increase in mRNA expression of both type I and type III collagen after MI from day three onwards. The maximal increase in colligin protein in the infarct area coincided with the most pronounced expression of collagen I and collagen III mRNA expression. Also, the expression and activity of matrix metalloproteinases (MMPs) and of tissue inhibitor of matrix metalloproteinase (TIMP)-2 mRNA were increased predominantly in the infarct area. TGF beta(1)and TGF-beta(2)expression increased within the first days after MI, whereas TGF-beta(3)expression was elevated predominantly in the infarct area. This pronounced increase in TGF-beta(3)persisted up to 82 days and correlated positively with the parameters of ECM metabolism. Thus, the scar formation is an ongoing dynamic process in which TGF-beta(3)seems to play an active role in the complex ventricular remodeling.

Heat shock protein 47 is expressed in fibrous regions of human atheroma and Is regulated by growth factors and oxidized low-density lipoprotein

BACKGROUND

Heat shock protein 47 (Hsp47) is a stress protein that may act as a chaperone for procollagen. Its involvement in atherosclerosis is unknown.

METHODS AND RESULTS

Hsp47 expression in human coronary arteries was assessed by immunostaining. Strong focal expression was evident in atherosclerotic, but not normal, arteries and was prevalent in the collagenous regions. Double immunostaining revealed that all cells expressing type I procollagen also expressed Hsp47. Moreover, parallel regulation of proalpha1(I)collagen and Hsp47 mRNA expression occurred with cultured human smooth muscle cells stimulated with transforming growth factor-beta1 or fibroblast growth factor-2. However, a proportion of Hsp47-expressing cells in plaque did not express type I procollagen, and this pattern could be reproduced in culture. Heat shock and oxidized LDL stimulated the expression of Hsp47 mRNA by smooth muscle cells, without a concomitant rise in proalpha1(I)collagen expression.

CONCLUSIONS

These findings identify Hsp47 as a novel constituent of human coronary atheroma. Its localization to the fibrous cap, regulation by growth factors in parallel with type I procollagen, and selective upregulation by stress raise the possibility that Hsp47 is a determinant of plaque stability.

Procollagen folding and assembly: the role of endoplasmic reticulum enzymes and molecular chaperones

Procollagen assembly occurs within the endoplasmic reticulum, where the C-propeptide domains of three polypeptide alpha-chains fold individually, and then interact and trimerise to initiate folding of the triple helical region. This highly complex folding and assembly pathway requires the co-ordinated action of a large number of endoplasmic reticulum-resident enzymes and molecular chaperones. Disease-causing mutations in the procollagens disturb folding and assembly and lead to prolonged interactions with molecular chaperones, retention in the endoplasmic reticulum, and intracellular degradation. This review focuses predominantly on prolyl 1-hydroxylase, an essential collagen modifying enzyme, and HSP47, a collagen-specific binding protein, and their proposed roles as molecular chaperones involved in fibrillar procollagen folding and assembly, quality control, and secretion.

Intracellular retention of procollagen within the endoplasmic reticulum is mediated by prolyl 4-hydroxylase

The correct folding and assembly of proteins within the endoplasmic reticulum (ER) are prerequisites for subsequent transport from this organelle to the Golgi apparatus. The mechanisms underlying the ability of the cell to recognize and retain unassembled or malfolded proteins generally require binding to molecular chaperones within the ER. One classic example of this process occurs during the biosynthesis of procollagen. Here partially folded intermediates are retained and prevented from secretion, leading to a build up of unfolded chains within the cell. The accumulation of these partially folded intermediates occurs during vitamin C deficiency due to incomplete proline hydroxylation, as vitamin C is an essential co-factor of the enzyme prolyl 4-hydroxylase. In this report we show that this retention is tightly regulated with little or no secretion occurring under conditions preventing proline hydroxylation. We studied the molecular mechanism underlying retention by determining which proteins associate with partially folded procollagen intermediates within the ER. By using a combination of cross-linking and sucrose gradient analysis, we show that the major protein binding to procollagen during its biosynthesis is prolyl 4-hydroxylase, and no binding to other ER resident proteins including Hsp47 was detected. This binding is regulated by the folding status rather than the extent of hydroxylation of the chains demonstrating that this enzyme can recognize and retain unfolded procollagen chains and can release these chains for further transport once they have folded correctly.

Isolation and characterization of a rheumatoid arthritis-specific antigen (RA-A47) from a human chondrocytic cell line (HCS-2/8)

Two types of 47 kDa antigen specifically recognized by sera from rheumatoid arthritis (RA) patients were isolated from the membrane fraction of a human chondrosarcoma-derived chondrocytic cell line (HCS-2/8) by a 2-step procedure: preparative SDS-PAGE and reverse-phase HPLC. An N-terminal amino acid sequence in one of the 47 kDa antigens, named RA-A47, had 81% homology to that deduced from the DNA sequence of the colligin gene which is reported as human hsp47 gene, and 100% homology to that deduced from the DNA sequence of colligin-2 gene, a homologue of colligin. The RA-A47 cross-reacted with a monoclonal antibody raised against chick heat shock protein (Hsp) 47 and bound to gelatin. The expression of the ra-a47 gene was enhanced by heat shock treatment and TGF-beta stimulation. These findings suggest that RA-A47 is a Hsp47-like protein, presumably the product of the colligin-2 gene, and that a collagen-specific molecular chaperone(s) such as Hsp47 and/or RA-A47 is involved in cartilage destruction in RA.

Serpin alpha 1proteinase inhibitor probed by intrinsic tryptophan fluorescence spectroscopy

Various conformational forms of the archetypal serpin human alpha 1proteinase inhibitor (alpha 1PI), including ordered polymers, active and inactive monomers, and heterogeneous aggregates, have been produced by refolding from mild denaturing conditions. These forms presumably originate by different folding pathways during renaturation, under the influence of the A and C sheets of the molecule. Because alpha 1PI contains only two Trp residues, at positions 194 and 238, it is amenable to fluorescence quenching resolved spectra and red-edge excitation measurements of the Trp environment. Thus, it is possible to define the conformation of the various forms based on the observed fluorescent properties of each of the Trp residues measured under a range of conditions. We show that denaturation in GuHCl, or thermal denaturation in Tris, followed by renaturation, leads to the formation of polymers that contain solvent-exposed Trp 238, which we interpret as ordered head-to-tail polymers (A-sheet polymers). However, thermal denaturation in citrate leads to shorter polymers where some of the Trp 238 residues are not solvent accessible, which we interpret as polymers capped by head-to-head interactions via the C sheet. The latter treatment also generates monomers thought to represent a latent form, but in which the environment of Trp 238 is occluded by ionized groups. These data indicate that the folding pathway of alpha 1PI, and presumably other serpins, is sensitive to solvent composition that affects the affinity of the reactive site loop for the A sheet or the C sheet.