Electrospun Scaffold of Collagen and Polycaprolactone Containing ZnO Quantum Dots for Skin Wound Regeneration

Nanofibers(NFs)have been widely used in tissue engineering such as wound healing.In this work,the antibacterial ZnO quantum dots(ZnO QDs)have been incorporated into the biocompatible poly(ε-caprolactone)/collagen(PCL/Col)fibrous scaffolds for wound healing.The as-fabricated PCL-Col/ZnO fibrous scaffolds exhibited good swelling,antibacterial activity,and biodegradation behaviors,which were beneficial for the applications as a wound dressing.Moreover,the PCL-Col/ZnO fibrous scaffolds showed excellent cytocompatibility for promoting cell proliferation.The resultant PCL-Col/ZnO fibrous scaffolds containing vascular endothelial growth factor(VEGF)also exhibited promoted wound-healing effect through promoting expression of transforming growth factor-β(TGF-β)and the vascular factor(CD31)in tissues in the early stages of wound healing.This new electrospun fibrous scaffolds with wound-healing promotion and antibacterial property should be convenient for treating wound healing.     

All roads lead to Rome (but some may be harder to travel): SRP-independent translocation into the endoplasmic reticulum

Abstract

Translocation into the endoplasmic reticulum (ER) is the first biogenesis step for hundreds of eukaryotic secretome proteins. Over the past 30 years, groundbreaking biochemical, structural and genetic studies have delineated one conserved pathway that enables ER translocation- the signal recognition particle (SRP) pathway. However, it is clear that this is not the only pathway which can mediate ER targeting and insertion. In fact, over the past decade, several SRP-independent pathways have been uncovered, which recognize proteins that cannot engage the SRP and ensure their subsequent translocation into the ER. These SRP-independent pathways face the same challenges that the SRP pathway overcomes: chaperoning the preinserted protein while in the cytosol, targeting it rapidly to the ER surface and generating vectorial movement that inserts the protein into the ER. This review strives to summarize the various mechanisms and machineries which mediate these stages of SRP-independent translocation, as well as examine why SRP-independent translocation is utilized by the cell. This emerging understanding of the various pathways utilized by secretory proteins to insert into the ER draws light to the complexity of the translocational task, and underlines that insertion into the ER might be more varied and tailored than previously appreciated.     

Molecular Chaperones HscA/Ssq1 and HscB/Jac1 and Their Roles in Iron-Sulfur Protein Maturation

ABSTRACT

Genetic and biochemical studies have led to the identification of several cellular pathways for the biosynthesis of iron-sulfur proteins in different organisms. The most broadly distributed and highly conserved system involves an Hsp70 chaperone and J-protein co-chaperone system that interacts with a scaffold-like protein involved in [FeS]-cluster preassembly. Specialized forms of Hsp70 and their co-chaperones have evolved in bacteria (HscA, HscB) and in certain fungi (Ssq1, Jac1), whereas most eukaryotes employ a multifunctional mitochondrial Hsp70 (mtHsp70) together with a specialized co-chaperone homologous to HscB/Jac1. HscA and Ssq1 have been shown to specifically bind to a conserved sequence present in the [FeS]-scaffold protein designated IscU in bacteria and Isu in fungi, and the crystal structure of a complex of a peptide containing the IscU recognition region bound to the HscA substrate binding domain has been determined. The interaction of IscU/Isu with HscA/Ssq1 is regulated by HscB/Jac1 which bind the scaffold protein to assist delivery to the chaperone and stabilize the chaperone-scaffold complex by enhancing chaperone ATPase activity. The crystal structure of HscB reveals that the N-terminal J-domain involved in regulation of HscA ATPase activity is similar to other J-proteins, whereas the C-terminal domain is unique and appears to mediate specific interactions with IscU. At the present time the exact function(s) of chaperone-[FeS]-scaffold interactions in iron-sulfur protein biosynthesis remain(s) to be established. In vivo and in vitro studies of yeast Ssq1 and Jac1 indicate that the chaperones are not required for [FeS]-cluster assembly on Isu. Recent in vitro studies using bacterial HscA, HscB and IscU have shown that the chaperones destabilize the IscU[FeS] complex and facilitate cluster delivery to an acceptor apo-protein consistent with a role in regulating cluster release and transfer. Additional genetic and biochemical studies are needed to extend these findings to mtHsp70 activities in higher eukaryotes.     

C-terminus of Hsc70-interacting protein (CHIP) enhances stemness properties of human Wharton’s jelly mesenchymal stem cell

Mesenchymal stem cells are an attractive source of multipotent cells in part because they are easy to obtain. Several E3 ligases regulate the stability and functions of various factors in different adult stem cells through the ubiquitylation pathway. We investigated the C-terminus of Hsc70-interacting protein (CHIP) E3 ligase that regulates pluripotency of human Wharton’s jelly mesenchymal stem cells (hWJMSC). We found that CHIP increases protein kinase B (Akt) phosphorylation by decreased expression of phosphatase and tensin homolog (PTEN), which suggests improvement of the survival pathway by CHIP over-expression. We also found that increased CHIP expression induced Sox2 and NANOG, which can promote stem cell self-renewal and prevent oxidative stress-induced senescence of hWJMSC by decreased p21. We found that CHIP could be used to enhance the multiple functions of hWJMSC.     

Constitutive heat shock protein 70 interacts with α-enolase and protects cardiomyocytes against oxidative stress

Abstract

Constitutive heat shock protein 70 (Hsc70) is a molecular chaperone that has been shown to protect cardiomyocytes against oxidative stress. However, the molecular mechanism responsible for this protection remains uncertain. To understand the mechanism associated with the myocardial protective role of Hsc70, we have embarked upon a systematic search for Hsc70-interacting proteins. Using adenosine diphosphate (ADP) affinity chromatography and mass spectrometry, we have identified α-enolase, a rate-limiting enzyme in glycolysis, as a novel Hsc70-interacting protein in the myocardium of both sham and myocardial ischemia-reperfused Sprague–Dawley rat hearts. This interaction was confirmed by co-immunoprecipitation (IP) assays in the myocardial tissues and H9c2 cardiomyocytes and protein overlay assay (POA). It was further shown that Hsc70-overexpression alleviated the H₂O₂-induced decrease of α-enolase activity and cell damage, and Hsc70 deficiency aggravated the decrease of α-enolase activity and cell damage in H₂O₂ treated H9c2 cells. Our research suggests that the protective effect of Hsc70 on the cardiomyocytes against oxidative stress is partly associated with its interaction with α-enolase.     

Induction of heat shock proteins in cerebral cortical cultures by celastrol

Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis (ALS) are ‘protein misfolding disorders’ of the mature nervous system that are characterized by the accumulation of protein aggregates and selective cell loss. Different brain regions are impacted, with Alzheimer’s affecting cells in the cerebral cortex, Parkinson’s targeting dopaminergic cells in the substantia nigra and ALS causing degeneration of cells in the spinal cord. These diseases differ widely in frequency in the human population. Alzheimer’s is more frequent than Parkinson’s and ALS. Heat shock proteins (Hsps) are ‘protein repair agents’ that provide a line of defense against misfolded, aggregation-prone proteins. We have suggested that differing levels of constitutively expressed Hsps (Hsc70 and Hsp27) in neural cell populations confer a variable buffering capacity against ‘protein misfolding disorders’ that correlates with the relative frequencies of these neurodegenerative diseases. The high relative frequency of Alzheimer’s may due to low levels of Hsc70 and Hsp27 in affected cell populations that results in a reduced defense capacity against protein misfolding. Here, we demonstrate that celastrol, but not classical heat shock treatment, is effective in inducing a set of neuroprotective Hsps in cultures derived from cerebral cortices, including Hsp70, Hsp27 and Hsp32. This set of Hsps is induced by celastrol at ‘days in vitro’ (DIV) 13 when cultured cortical cells reached maturity. The inducibility of a set of neuroprotective Hsps in mature cortical cultures at DIV13 suggests that celastrol is a potential agent to counter Alzheimer’s disease, a neurodegenerative ‘protein misfolding disorder’ of the adult brain that targets cells in the cerebral cortex.