唾液酸生物学与人类健康和疾病

唾液酸（sialicacid）是一类酸性九碳单糖,是所有神经氨酸或酮基一脱氧壬酮糖酸（KDN）的N-或O-衍生物的总称。唾液酸作为复合糖的组成部分镶嵌于所有细胞表面以及人多数脊椎动物糖蛋白和糖脂分予的末端最外侧。唾液酸家族成员已经达到五十多个,其分子结构多样,在生物体内分布广泛。唾液酸介导或调制了发育、炎症、病原感染、肿瘤发生发展等诸多生理和病理过程,与人类健康和疾病密切关联。对唾液酸生物学的研究已成为糖生物学研究的热点之一。对唾液酸与人类健康与疾病研究的新进展做一综述。     

Generation of transgenic monkeys with human inherited genetic disease

Modeling human diseases using nonhuman primates including chimpanzee, rhesus, cynomolgus, marmoset and squirrel monkeys has been reported in the past decades. Due to the high similarity between nonhuman primates and humans, including genome constitution, cognitive behavioral functions, anatomical structure, metabolic, reproductive, and brain functions; nonhuman primates have played an important role in understanding physiological functions of the human body, clarifying the underlying mechanism of human diseases, and the development of novel treatments for human diseases. However, nonhuman primate research has been restricted to cognitive, behavioral, biochemical and pharmacological approaches of human diseases due to the limitation of gene transfer technology in nonhuman primates. The recent advancement in transgenic technology that has led to the generation of the first transgenic monkey in 2001 and a transgenic monkey model of Huntington’s disease (HD) in 2008 has changed that focus. The creation of transgenic HD monkeys that replicate key pathological features of human HD patients further suggests the crucial role of nonhuman primates in the future development of biomedicine. These successes have opened the door to genetic manipulation in nonhuman primates and a new era in modeling human inherited genetic disorders. We focused on the procedures in creating transgenic Huntington’s disease monkeys, but our work can be applied to transgenesis in other nonhuman primate species.     

Stable nonviral genetic correction of inherited human skin disease

Current gene-transfer technologies display limitations in achieving effective gene delivery. Among these limitations are difficulties in stably integrating large corrective sequences into the genomes of long-lived progenitor-cell populations. Current larger-capacity viral vectors suffer from biosafety concerns, whereas plasmid-based approaches have poor efficiency of stable gene transfer. These barriers hinder genetic correction of many severe inherited human diseases, such as the blistering skin disorder recessive dystrophic epidermolysis bullosa (RDEB), caused by mutations in the large COL7A1 gene. To circumvent these barriers, we used the phi C31 bacteriophage integrase, which stably integrates large DNA sequences containing a specific 285-base-pair attB sequence into genomic 'pseudo-attP sites'. phi C31 integrase-based gene transfer stably integrated the COL7A1 cDNA into genomes of primary epidermal progenitor cells from four unrelated RDEB patients. Skin regenerated using these cells displayed stable correction of hallmark RDEB disease features, including Type VII collagen protein expression, anchoring fibril formation and dermal-epidermal cohesion. These findings establish a practical approach to nonviral genetic correction of severe human genetic disorders requiring stable genomic integration of large DNA sequences.     

tRNA fragments in human health and disease

Transfer RNA (tRNA) is traditionally considered to be an adaptor molecule that helps ribosomes to decode messenger RNA (mRNA) and synthesize protein. Recent studies have demonstrated that tRNAs also serve as a major source of small non-coding RNAs that possess distinct and varied functions. These tRNA fragments are heterogeneous in size, nucleotide composition, biogenesis and function. Here we describe multiple roles that tRNA fragments play in cell physiology and discuss their relevance to human health and disease.     

Sialic acids in human health and disease

The surfaces of all vertebrate cells are decorated with a dense and complex array of sugar chains, which are mostly attached to proteins and lipids. Most soluble secreted proteins are also similarly decorated with such glycans. Sialic acids are a diverse family of sugar units with a nine-carbon backbone that are typically found attached to the outermost ends of these chains. Given their location and ubiquitous distribution, sialic acids can mediate or modulate a wide variety of physiological and pathological processes. This review considers some examples of their established and newly emerging roles in aspects of human physiology and disease.     

Mitochondrial creatine kinase in human health and disease

Mitochondrial creatine kinase (MtCK), together with cytosolic creatine kinase isoenzymes and the highly diffusible CK reaction product, phosphocreatine, provide a temporal and spatial energy buffer to maintain cellular energy homeostasis. Mitochondrial proteolipid complexes containing MtCK form microcompartments that are involved in channeling energy in form of phosphocreatine rather than ATP into the cytosol. Under situations of compromised cellular energy state, which are often linked to ischemia, oxidative stress and calcium overload, two characteristics of mitochondrial creatine kinase are particularly relevant: its exquisite susceptibility to oxidative modifications and the compensatory up-regulation of its gene expression, in some cases leading to accumulation of crystalline MtCK inclusion bodies in mitochondria that are the clinical hallmarks for mitochondrial cytopathies. Both of these events may either impair or reinforce, respectively, the functions of mitochondrial MtCK complexes in cellular energy supply and protection of mitochondria form the so-called permeability transition leading to apoptosis or necrosis.     

The nuclear lamina and inherited disease

Inherited disorders of the nuclear lamina present some of the most intriguing puzzles in cell biology. Mutations in lamin A and lamin C – nuclear intermediate filament proteins that are expressed in nearly all somatic cells – cause tissue-specific diseases that affect striated muscle, adipose tissue and peripheral nerve or skeletal development. Recent studies provide clues about how different mutations in these proteins cause either muscle disease or partial lipodystrophy. Although the precise pathogenic mechanisms are currently unknown, the involvement of lamins in several different disorders shows that research on the nuclear lamina will shed light on common human pathologies.     

An usage of cultured human cell lines in studies of inherited metabolic disease

Cultured skin fibroblasts and lymphoblastoid lines (established by Epstein-Barr infection) derived from patients have been commonly used in studies on inherited metabolic disorders. It is generally accepted that, on some occasions, valuable information for comprehending the normal transport function and intracellular metabolism in human cells only becomes available through studies using affected cells, and not normal cells. Besides clarification of the mechanism an abnormal function caused by a mutant enzyme, cultured cells provide other useful information (or products), with advanced procedures including cell fusion and gene technology; genetic heterogeneity (gene complementation analysis), correction of mutant genes (transfer of genes or gene products), gene cloning of a specific locus (using chromosomal deletion) and gene expression. The application of "reverse genetics" may permit further access to a complex cellular system.     

Golgi glycosylation and human inherited diseases

The Golgi factory receives custom glycosylates and dispatches its cargo to the correct cellular locations. The process requires importing donor substrates, moving the cargo, and recycling machinery. Correctly glycosylated cargo reflects the Golgi's quality and efficiency. Genetic disorders in the specific equipment (enzymes), donors (nucleotide sugar transporters), or equipment recycling/reorganization components (COG, SEC, golgins) can all affect glycosylation. Dozens of human glycosylation disorders fit these categories. Many other genes, with or without familiar names, well-annotated pedigrees, or likely homologies will join the ranks of glycosylation disorders. Their broad and unpredictable case-by-case phenotypes cross the traditional medical specialty boundaries. The gene functions in patients may be elusive, but their common feature may include altered glycosylation that provide clues to Golgi function. This article focuses on a group of human disorders that affect protein or lipid glycosylation. Readers may find it useful to generalize some of these patient-based, translational observations to their own research.     

Toxicoproteomics in human health and disease: an update

Introduction: Toxicoproteomics is an emerging area of omics, intended to explore the changes in protein expression and modifications in biological samples exposed to toxicants. The development of techniques that utilize sophisticated instruments in proteomics has facilitated the exploration of a wide-range of protein coverage and assisted the quantitative and qualitative evaluation of protein changes as a result of the toxic effects of toxic substances.

Areas covered: Studies on toxicoproteomics have an immense potential to explore the molecular mechanism of action of a variety of toxic substances through deciphering the proteomic map altered as a result of toxicant exposure. Here, we provide an overview of toxicoproteomic approaches and the current paradigm of toxicoproteomics.

Expert commentary: Research in this area continues to increase our understanding of the role of toxicants in worsening human health and toxicity driven diseases. The progress in toxicoproteomics may realize the development of novel biomarkers, drug targets and personalized medicines by incorporating the advanced proteomic applications in this field.     

The human mitochondrial replication fork in health and disease

Mitochondria are organelles whose main function is to generate power by oxidative phosphorylation. Some of the essential genes required for this energy production are encoded by the mitochondrial genome, a small circular double stranded DNA molecule. Human mtDNA is replicated by a specialized machinery distinct from the nuclear replisome. Defects in the mitochondrial replication machinery can lead to loss of genetic information by deletion and/or depletion of the mtDNA, which subsequently may cause disturbed oxidative phosphorylation and neuromuscular symptoms in patients. We discuss here the different components of the mitochondrial replication machinery and their role in disease. We also review the mode of mammalian mtDNA replication.     

Mitochondrial protein import and human health and disease

The targeting and assembly of nuclear-encoded mitochondrial proteins are essential processes because the energy supply of humans is dependent upon the proper functioning of mitochondria. Defective import of mitochondrial proteins can arise from mutations in the targeting signals within precursor proteins, from mutations that disrupt the proper functioning of the import machinery, or from deficiencies in the chaperones involved in the proper folding and assembly of proteins once they are imported. Defects in these steps of import have been shown to lead to oxidative stress, neurodegenerative diseases, and metabolic disorders. In addition, protein import into mitochondria has been found to be a dynamically regulated process that varies in response to conditions such as oxidative stress, aging, drug treatment, and exercise. This review focuses on how mitochondrial protein import affects human health and disease.     

Autoantibodies to alpha-synuclein in inherited Parkinson's disease

Neurodegeneration in Parkinson's disease (PD) is accompanied by a local immune reaction in the affected brain regions. It is well established that alpha-synuclein is directly implicated in the pathogenesis of PD. Development of the disease is often associated with changes of expression and cellular compartmentalisation of this protein; moreover, its oligomers or protofibrils are often released to the CSF and plasma of patients. Aggregated alpha-synuclein can trigger the activation of microglia; however, its capacity to induce production of specific autoantibodies (AAb) has not been assessed. In this study, we examined the presence of AAb against synuclein family members in the peripheral blood serum of PD patients and control individuals. Presence of AAb against beta-synuclein or gamma-synuclein showed no association with PD. Multi-epitopic AAb against alpha-synuclein were detected in 65% of all patients tested and their presence strongly correlated with an inherited mode of the disease but not with other disease-related factors. The frequency of the presence of AAb in the studied group of patients with sporadic form of PD was not significantly different from the frequency in the control group but very high proportion (90%) of patients with familial form of the disease were positive for AAb against alpha-synuclein. We hypothesise that these AAb could be involved in pathogenesis of the inherited form of PD.     

Troponin I phosphorylation in human myocardium in health and disease

Cardiac troponin I (cTnI) is well known as a biomarker for the diagnosis of myocardial damage. However, because of its central role in the regulation of contraction and relaxation in heart muscle, cTnI may also be a potential target for the treatment of heart failure. Studies in rodent models of cardiac disease and human heart samples showed altered phosphorylation at various sites on cTnI (i.e. site-specific phosphorylation). This is caused by altered expression and/or activity of kinases and phosphatases during heart failure development. It is not known whether these (transient) alterations in cTnI phosphorylation are beneficial or detrimental. Knowledge of the effects of site-specific cTnI phosphorylation on cardiomyocyte contractility is therefore of utmost importance for the development of new therapeutic strategies in patients with heart failure. In this review we focus on the role of cTnI phosphorylation in the healthy heart upon activation of the beta-adrenergic receptor pathway (as occurs during increased stress and exercise) and as a modulator of the Frank-Starling mechanism. Moreover, we provide an overview of recent studies which aimed to reveal the functional consequences of changes in cTnI phosphorylation in cardiac disease.     

Voluntary activation of the human diaphragm in health and disease

Intersubjectcomparison of the crural diaphragm electromyogram, as measured by anesophageal electrode, requires a reliable means for normalizing thesignal. The present study set out 1) to evaluate which voluntary respiratory maneuvers provide high andreproducible diaphragm electromyogram root-mean-square (RMS) values and2) to determine the relativediaphragm activation and mechanical and ventilatory outputs duringbreathing at rest in healthy subjects(n = 5), in patients with severechronic obstructive pulmonary disease (COPD,n = 5), and in restrictive patientswith prior polio infection (PPI, n = 6). In all groups, mean voluntary maximal RMS values were higher duringinspiration to total lung capacity than during sniff inhalation throughthe nose (P = 0.035, ANOVA). The RMS(percentage of voluntary maximal RMS) during quiet breathing was 8% inhealthy subjects, 43% in COPD patients, and 45% in PPI patients.Despite the large difference in relative RMS(P = 0.012), there were no differencesin mean transdiaphragmatic pressure (P = 0.977) and tidal volumes (P = 0.426). We conclude that voluntary maximal RMS is reliably obtainedduring an inspiration to total lung capacity but a sniff inhalationcould be a useful complementary maneuver. Severe COPD and PPI patientsbreathing at rest are characterized by increased diaphragm activationwith no change in diaphragm pressure generation.