Nucleoside diphosphate kinase A as a controller of AMP-kinase in airway epithelia

This review integrates recent understanding of a novel role for NDPK-A in two related directions: Firstly, its role in an airway epithelial cell when bound to the luminal (apical) membrane and secondly in the cytosol of many different cells (epithelial and non-epithelial) where an isoform-specific interaction occurs with a regulatory partner, AMPKα1. Thus NDPK-A is present in both a membrane and cytosolic environment but in the apical membrane, its roles are not understood in detail; preliminary data suggest that it co-localises with the cystic fibrosis protein (CFTR). In cytosol, we find that NDPK-A is coupled to the catalytic alpha1 isoform of the AMP-activated protein kinase (AMPKα subunit), which is part of a heterotrimeric protein complex that responds to cellular energy status by switching off ATP-consuming pathways and switching on ATP-generating pathways when ATP is limiting. We find that ATP is located within this complex and ‘fed’ from NDPK to AMPK without ever ‘seeing’ bulk solution. Importantly, the reverse can also happen such that AMPK activity can be made to decline when NDPK-A ‘steals’ ATP from AMPK. Thus we propose a novel paradigm in NDPK-A function by suggesting that AMP-kinase can be regulated by NDPK-A, independently of AMP

Ethnic Identity of Older Chinese in Canada

In Canada’s multicultural society, ethnic identity is important to the elderly and can influence areas such as access to services, health promotion and care. Often, the complex nature of ethnic identity is underestimated when looking at cultural groups. This study aims to: (a) validate the factor structure of a Chinese ethnic identity measure for older Chinese in Canada, (b) examine the level of ethnic identity of the participants, and (c) examine the correlates of ethnic identity in these older individuals. Using data from a large, national research project on the elderly Chinese in Canada, this study analyzed the results gathered from a total of 2,272 participants. Principal component analysis, maximum-likelihood confirmatory factor analysis, and multiple regression analysis were performed. The results indicated that ethnic identity of the older Chinese is a multi-dimensional construct made up of three factors: (a) culture related activities, (b) community ties, (c) linkage with country of origin, and (d) cultural identification. The findings have provided a better understanding of how ethnic identity can be measured among the aging Chinese population in Canada

The cystic fibrosis transmembrane recruiter the alter ego of CFTR as a multi-kinase anchor

This review focuses on a newly discovered interaction between protein kinases involved in cellular energetics, a process that may be disturbed in cystic fibrosis for unknown reasons. I propose a new model where kinase-mediated cellular transmission of energy provides mechanistic insight to a latent role of the cystic fibrosis transmembrane conductance regulator (CFTR). I suggest that CFTR acts as a multi-kinase recruiter to the apical epithelial membrane. My group finds that, in the cytosol, two protein kinases involved in cell energy homeostasis, nucleoside diphosphate kinase (NDPK) and AMP-activated kinase (AMPK), bind one another. Preliminary data suggest that both can also bind CFTR (function unclear). The disrupted role of this CFTR-kinase complex as ‘membrane transmitter to the cell’ is proposed as an alternative paradigm to the conventional ion transport mediated and CFTR/chloride-centric view of cystic fibrosis pathogenesis. Chloride remains important, but instead, chloride-induced control of the phosphohistidine content of one kinase component (NDPK, via a multi-kinase complex that also includes a third kinase, CK2; formerly casein kinase 2). I suggest that this complex provides the necessary near-equilibrium conditions needed for efficient transmission of phosphate energy to proteins controlling cellular energetics. Crucially, a new role for CFTR as a kinase controller is proposed with ionic concentration acting as a signal. The model posits a regulatory control relay for energy sensing involving a cascade of protein kinases bound to CFTR

Glycosaminoglycans and Sialylated Glycans Sequentially Facilitate Merkel Cell Polyomavirus Infectious Entry

Merkel cell polyomavirus (MCV or MCPyV) appears to be a causal factor in the development of Merkel cell carcinoma, a rare but highly lethal form of skin cancer. Although recent reports indicate that MCV virions are commonly shed from apparently healthy human skin, the precise cellular tropism of the virus in healthy subjects remains unclear. To begin to explore this question, we set out to identify the cellular receptors or co-receptors required for the infectious entry of MCV. Although several previously studied polyomavirus species have been shown to bind to cell surface sialic acid residues associated with glycolipids or glycoproteins, we found that sialylated glycans are not required for initial attachment of MCV virions to cultured human cell lines. Instead, glycosaminoglycans (GAGs), such as heparan sulfate (HS) and chondroitin sulfate (CS), serve as initial attachment receptors during the MCV infectious entry process. Using cell lines deficient in GAG biosynthesis, we found that N-sulfated and/or 6-O-sulfated forms of HS mediate infectious entry of MCV reporter vectors, while CS appears to be dispensable. Intriguingly, although cell lines deficient in sialylated glycans readily bind MCV capsids, the cells are highly resistant to MCV reporter vector-mediated gene transduction. This suggests that sialylated glycans play a post-attachment role in the infectious entry process. Results observed using MCV reporter vectors were confirmed using a novel system for infectious propagation of native MCV virions. Taken together, the findings suggest a model in which MCV infectious entry occurs via initial cell binding mediated primarily by HS, followed by secondary interactions with a sialylated entry co-factor. The study should facilitate the development of inhibitors of MCV infection and help shed light on the infectious entry pathways and cellular tropism of the virus

Stress, ageing and their influence on functional, cellular and molecular aspects of the immune system

The immune response is essential for keeping an organism healthy and for defending it from different types of pathogens. It is a complex system that consists of a large number of components performing different functions. The adequate and controlled interaction between these components is necessary for a robust and strong immune response. There are, however, many factors that interfere with the way the immune response functions. Stress and ageing now consistently appear in the literature as factors that act upon the immune system in the way that is often damaging. This review focuses on the role of stress and ageing in altering the robustness of the immune response first separately, and then simultaneously, discussing the effects that emerge from their interplay. The special focus is on the psychological stress and the impact that it has at different levels, from the whole system to the individual molecules, resulting in consequences for physical health

Compensatory proteome adjustments imply tissue-specific structural and metabolic reorganization following episodic hypoxia or anoxia in the epaulette shark (Hemiscyllium ocellatum)

The epaulette shark (Hemiscyllium ocellatum) represents an ancestral vertebrate model of episodic hypoxia and anoxia tolerance at tropical temperatures. We used two-dimensional gel electrophoresis and mass spectrometry-based proteomics approaches, combined with a suite of physiological measures, to characterize this species' responses to 1) one episode of anoxia plus normoxic recovery, 2) one episode of severe hypoxia plus recovery, or 3) two episodes of severe hypoxia plus recovery. We examined these responses in the cerebellum and rectal gland, two tissues with high ATP requirements. Sharks maintained plasma ionic homeostasis following all treatments, and activities of Na+/K+-ATPase and caspase 3/7 in both tissues were unchanged. Oxygen lack and reoxygenation elicited subtle adjustments in the proteome. Hypoxia led to more extensive proteome responses than anoxia in both tissues. The cerebellum and rectal gland exhibited treatment-specific responses to oxygen limitation consistent with one or more of several strategies: 1) neurotransmitter and receptor downregulation in cerebellum to prevent excitotoxicity, 2) cytoskeletal/membrane reorganization, 3) metabolic reorganization and more efficient intracellular energy shuttling that are more consistent with sustained ATP turnover than with long-term metabolic depression, 4) detoxification of metabolic byproducts and oxidative stress in light of continued metabolic activity, particularly following hypoxia in rectal gland, and 5) activation of prosurvival signaling. We hypothesize that neuronal morphological changes facilitate prolonged protection from excitotoxicity via dendritic spine remodeling in cerebellum (i.e., synaptic structural plasticity). These results recapitulate several highly conserved themes in the anoxia and hypoxia tolerance, preconditioning, and oxidative stress literature in a single system. In addition, several of the identified pathways and proteins suggest potentially novel mechanisms for enhancing anoxia or hypoxia tolerance in vertebrates. Overall, our data show that episodic hypoxic or anoxic exposure and recovery in the epaulette shark amplifies a constitutive suite of compensatory mechanisms that further prepares them for subsequent insults