Thermosensitive biomimetic polyisocyanopeptide hydrogels may facilitate wound repair

Changing wound dressings inflicts pain and may disrupt wound repair. Novel synthetic thermosensitive hydrogels based on polyisocyanopeptide (PIC) offer a solution. These gels are liquid below 16 °C and form gels beyond room temperature. The architecture and mechanical properties of PIC gels closely resemble collagen and fibrin, and include the characteristic stiffening response at high strains. Considering the reversible thermo-responsive behavior, we postulate that PIC gels are easy to apply and remove, and facilitate healing without eliciting foreign body responses or excessive inflammation. Biocompatibility may be higher in RGD-peptide-functionalized PIC gels due to enhanced cell binding capabilities. Full-thickness dorsal skin wounds in mice were compared to wounds treated with PIC gel and PIC-RGD gel for 3 and 7 days. No foreign body reactions and similar wound closure rates were found in all groups. The level of macrophages, myofibroblasts, epithelial migration, collagen expression, and blood vessels did not significantly differ from controls. Surprisingly, granulocyte populations in the wound decreased significantly in the PIC gel-treated groups, likely because foreign bacteria could not penetrate the gel. RGD-peptides did not further improve any effect observed for PIC. The absence of adverse effects, ease of application, and the possibilities for bio-functionalization make the biomimetic PIC hydrogels suitable for development into wound dressings

p25α Relocalizes in Oligodendroglia from Myelin to Cytoplasmic Inclusions in Multiple System Atrophy

p25α is an oligodendroglial protein that can induce aggregation of α-synuclein and accumulates in oligodendroglial cell bodies containing fibrillized α-synuclein in the neurodegenerative disease multiple system atrophy (MSA). We demonstrate biochemically that p25α is a constituent of myelin and a high-affinity ligand for myelin basic protein (MBP), and in situ immunohistochemistry revealed that MBP and p25α colocalize in myelin in normal human brains. Analysis of MSA cases reveals dramatic changes in p25α and MBP throughout the course of the disease. In situ immunohistochemistry revealed a cellular redistribution of p25α immunoreactivity from the myelin to the oligodendroglial cell soma, with no overall change in p25α protein concentration using immunoblotting. Concomitantly, an ∼80% reduction in the concentration of full-length MBP protein was revealed by immunoblotting along with the presence of immunoreactivity for MBP degradation products in oligodendroglia. The oligodendroglial cell bodies in MSA displayed an enlargement along with the relocalization of p25α, and this was enhanced after the deposition of α-synuclein in the glial cytoplasmic inclusions. Overall, the data indicate that changes in the cellular interactions between MBP and p25α occur early in MSA and contribute to abnormalities in myelin and subsequent α-synuclein aggregation and the ensuing neuronal degeneration that characterizes this disease

p25α is flexible but natively folded and binds tubulin with oligomeric stoichiometry

p25α is a 219-residue proteinwhich stimulates aberrant tubulin polymerization and is implicated in a variety of other functions. The protein has unusual secondary structure involving significant amounts of random coil, and binding to microtubules is accompanied by a large structural change, suggesting a high degree of plasticity. p25α has been proposed to be natively unfolded, so that folding is coupled to interaction with its physiological partners. Here we show that recombinant human p25α is folded under physiological conditions, since it has a well structured and solvent-sequestered aromatic environment and considerable chemical shift dispersion of amide and aliphatic protons. With increasing urea concentrations, p25α undergoes clear spectral changes suggesting significant loss of structure. p25α unfolds cooperatively in urea according to a simple two-state transition with a stability in water of ~5 kcal/mol. The protein behaves as a monomer and refolds with a transient on-pathway folding intermediate. However, high sensitivity to proteolytic attack and abnormal gel filtration migration behavior suggests a relatively extended structure, possibly organized in distinct domains. A deletion mutant of p25α lacking residues 3–43 also unfolds cooperatively and with similar stability, suggesting that the N-terminal region is largely unstructured. Both proteins undergo significant loss of structure when bound to monomeric tubulin. The stoichiometry of binding is estimated to be 3–4 molecules of tubulin per p25α and is not significantly affected by the deletion of residues 3–43. In conclusion, we dismiss the proposal that p25α is natively unfolded, although the protein is relatively flexible. This flexibility may be linked to its tubulin-binding properties