No abstract

Ion transport characteristics across a macrocoacervate layer membrane composed of aqueous elastin model polypeptides with a specific repeating pentapeptide sequence, H‐(Val‐Pro‐Gly‐Val‐Gly)n‐Val‐OMe (n ≥ 40), were investigated. Transmembrane potential responses for NaCl, MgCl2, and CaCl2 concentration‐cell systems were measured and examined systematically by comparing with those across a coacervate membrane composed of bovine neck ligamental α‐elastin. In the case of the NaCl and MgCl2 systems, potential responses across these protein liquid membranes were different noticeably from each other depending upon the molecular structure with and without charged peptide side chains, whereas in the CaCl2 systems the transmembrane potential responses across the noncharged polypentapeptide coacervate membrane were comparable with those across the α‐elastin coacervate membrane carrying both the positively and negatively charged amino acid residues as an amphoteric ion‐exchange membrane. These results indicated that mechanisms of major Ca2+ ion transport are based on the specific and selective interactions with electrically neutral sites of elastin, such as the polypentapeptide backbone chain. © 1996 John Wiley & Sons, Inc.

Synthetic elastin peptides, VPGVG or its polymer (VPGVG),, enhanced the proliferation of smooth muscle cells 1.5-fold during 48 h treatment at the concetrations over 10 -6 M or 1.0 pg/ml, respectively. Monomeric and polymeric VPGVG sequences reduced elastin synthesis and its mRNA level to onethird and one-half of control respectively under the conditions in which the proliferation of cells were enhanced, but did not change collagen synthesis as measured by bacterial collagenase digestion. The elastin-specific autoregulation by elastin fragments may reflect the feedback regulation of elastin expression which may play an essential role in elastin metabolism under the normal and diseased conditions.

A protein liquid membrane composed of coacervated alpha-elastin, a chemical fragmentation product of the biological elastic fiber protein, functioned as an amphoteric liquid ion-exchange membrane. Ionic permselectivities of the alpha-elastin coacervate membrane to a series of metal chlorides were investigated for the concentration-cell systems by the ordinary electrochemical measurements. Effects of pH on the transmembrane potential responses for NaCl, CaCl2, and MgCl2 systems were examined. Only in the Ca(2+)-containing system did potential responses stay at constant levels against the pH changes, whereas in the other systems, increasing pH caused potential changes, indicating an improvement of cationic permselectivity across the alpha-elastin coacervate membrane. It was suggested that the characteristic Ca2+ transport mechanisms across the alpha-elastin coacervate membrane are related in some way to the polypeptide backbone interactions specific and selective to Ca2+ ions.

alpha-Elastin with an average molecular mass of 70 kDa, an oxalic acid fragmentation product of highly purified insoluble elastin, induced the migration of macrophages, with maximum activity at 10(-1) microg/ml. Relative to the positive control of 10(-8) M N-formylmethionyl-leucyl-phenylalanine (fMLP), the responsiveness of macrophages to alpha-elastin was nearly the same. Checkerboard analysis demonstrated that the cell movement is chemotaxis and not chemokinesis. A homologous deactivation test showed the possibility of the existence of alpha-elastin-recognizing sites on macrophages. In connection with macrophage chemotaxis in response to alpha-elastin, the intracellular signaling pathway was examined. The guanosine 3', 5'-cyclic monophosphate (cGMP) level was enhanced in macrophages stimulated by alpha-elastin, whereas the adenosine 3',5'-cyclic monophosphate (cAMP) level was not. Chemotaxis assaying of macrophages treated with 8-Br cGMP- and dibutyryl cAMP-loaded macrophages indicated that cGMP promotes cell movement and cAMP suppresses cell locomotion. The possible involvement of protein kinases in the alpha-elastin signaling pathway was explored by use of inhibitors specific for cGMP-dependent protein kinase (PKG), cAMP-dependent protein kinase (PKA), protein kinase C (PKC), and tyrosine kinase. The macrophage chemotactic response to alpha-elastin was inhibited by the PKG inhibitor, but not by the PKA, PKC, or tyrosine kinase inhibitor. These results suggested that the increase in the cGMP level and the activation of PKG in macrophages are involved in alpha-elastin induced macrophage chemotaxis.

A 61-year-old man infected with hepatitis C virus developed urinary protein. Two-dimensional electrophoresis and immunoblotting of sera revealed no monoclonal proteins. Light microscopy and immunofluorescence of a kidney biopsy specimen demonstrated bubbling appearance and formation of spikes, associated with predominantly IgA1-lambda deposition, but not IgG, along glomerular capillary walls. Electron microscopy showed electron-dense deposits without any fibrillary structure located in the glomerular basement membrane. Seven months after the kidney biopsy, the patient had a surgical operation for rectal cancer. One year later, the urinary protein was still present. The present case is the first report of an IgA1-lambda-type monoclonal immunoglobulin deposition disease associated with membranous features.

An elastin‐derived peptide with an average molecular mass of 25 kDa was shown to induce monocyte chemotaxis at the optimal concentration of 10‐1 μg/ml. Homologous deactivation test showed that monocytes exposed to the elastin‐derived peptide at 10‐1 μg/ml lost their chemotactic responsiveness when reexposed to the same stimulus. In conjunction with chemotactic response to the elastin‐derived peptide, intracellular guanosine 3′, 5′‐monophosphate (cGMP) levels were enhanced but intracellular adenosine 3′, 5′‐monophosphate (cAMP) levels were not. The monocyte migration induced by the elastin‐derived peptide was inhibited by cGMP dependent protein kinase (PKG) inhibitor, but not by cAMP dependent protein kinase inhibitor and protein kinase C inhibitor. These results suggest that the elastin‐derived peptide induces monocyte chemotaxis by increasing the level of cGMP, followed by activating PKG.

SUMMARY: An elastin-derived peptide with an average molecular mass of 25 kDa was shown to induce monocyte chemotaxis at the optimal concentration of 10 -1 o,g/ml. Homologous deactivation test showed that monocytes exposed to the elastin-derived peptide at 10 "1 wg/ml lost their chemotactic responsiveness when reexposed to the same stimulus. In conjunction with chemotactic response to the elastin-derived peptide, intracellular guanosine 3', 5'-monophosphate (cGMP) levels were enhanced but intracellular adenosine 3', 5'-monophosphate (cAMP) levels were not. The monocyte migration induced by the elastinderived peptide was inhibited by cGMP dependent protein kinase (PKG) inhibitor, but not by cAMP dependent protein kinase inhibitor and protein kinase C inhibitor. These results suggest that the elastin-derived peptide induces monocyte chemotaxis by increasing the level of cGMP, followed by activating PKG.