The maintenance of cell metabolism and homeostasis is a fundamental characteristic of living organisms. In eukaryotes, mitochondria are the cornerstone of these life supporting processes, playing leading roles in a host of core cellular functions, including energy transduction, metabolic and calcium signalling, and supporting roles in a number of biosynthetic pathways. The possession of a discrete mitochondrial genome dictates that the maintenance of mitochondrial 'fitness' requires quality control mechanisms which involve close communication with the nucleus. This review explores the synergistic mechanisms that control mitochondrial quality and function and ensure cellular bioenergetic homeostasis. These include antioxidant defence mechanisms that protect against oxidative damage caused by reactive oxygen species, while regulating signals transduced through such free radicals. Protein homeostasis controls import, folding, and degradation of proteins underpinned by mechanisms that regulate bioenergetic capacity through the mitochondrial unfolded protein response. Autophagic machinery is recruited for mitochondrial turnover through the process of mitophagy. Mitochondria also communicate with the nucleus to exact specific transcriptional responses through retrograde signalling pathways. The outcome of mitochondrial quality control is not only reliant on the efficient operation of the core homeostatic mechanisms but also in the effective interaction of mitochondria with other cellular components, namely the nucleus. Understanding mitochondrial quality control and the interactions between the organelle and the nucleus will be crucial in developing therapies for the plethora of diseases in which the pathophysiology is determined by mitochondrial dysfunction. This article is part of a Special Issue entitled Frontiers of Mitochondrial Research.

Mutations in the GBA gene encoding glucocerebrosidase cause Gaucher disease (GD), the most prevalent of the lysosomal storage disorders (LSDs) and increase susceptibility to Parkinson disease (PD). Clinically the two disorders can present in a similar manner with analogous pathological features, suggesting mechanistic links between the two disease states. An increasing body of evidence implicates defects in quality control pathways in both, and suggests that LSDs, as a group, can be classed as disorders of autophagy. Using a mouse model of type II neuronopathic GD, we observed global defects in cellular quality control pathways in midbrain neurons and astrocytes. Our data suggest that downregulation of autophagy, mitophagy, and the ubiquitin-proteasome system (UPS) results in accumulation of dysfunctional and fragmented mitochondria, insoluble SNCA/α-synuclein deposits and ubiquitinated proteins. These observations show that dysfunction of cellular quality control pathways lead to impaired energy and free radical homeostasis, providing new insights into the mechanisms of neurodegeneration in GD and illuminating the links between GD and PD.

The eukaryotic cell possesses specialized pathways to turn over and degrade redundant proteins and organelles. Each pathway is unique and responsible for degradation of distinctive cytosolic material. The ubiquitin‐proteasome system and autophagy (chaperone‐mediated, macro, micro and organelle specific) act synergistically to maintain proteostasis. Defects in this equilibrium can be deleterious at cellular and organism level, giving rise to various disease states. Dysfunction of quality control pathways are implicated in neurodegenerative diseases and appear particularly important in Parkinson's disease and the lysosomal storage disorders. Neurodegeneration resulting from impaired degradation of ubiquitinated proteins and α‐synuclein is often accompanied by mitochondrial dysfunction. Mitochondria have evolved to control a diverse number of processes, including cellular energy production, calcium signalling and apoptosis, and like every other organelle within the cell, they must be ‘recycled.’ Failure to do so is potentially lethal as these once indispensible organelles become destructive, leaking reactive oxygen species and activating the intrinsic cell death pathway. This process is paramount in neurons which have an absolute dependence on mitochondrial oxidative phosphorylation as they cannot up‐regulate glycolysis. As such, mitochondrial bioenergetic failure can underpin neural death and neurodegenerative disease. In this review, we discuss the links between cellular quality control and neurodegenerative diseases associated with mitochondrial dysfunction, with particular attention to the emerging links between Parkinson's and Gaucher diseases in which defective quality control is a defining factor.Linked Articles: This article is part of a themed issue on Mitochondrial Pharmacology: Energy, Injury & Beyond. To view the other articles in this issue visit http://dx.doi.org/10.1111/bph.2014.171.issue‐8

Cancer cachexia is a common condition in many cancer patients, particularly those with advanced disease. Cancer cachexia patients are generally less tolerant to chemotherapies and radiotherapies, largely limiting their treatment options. While the search for treatments of this condition are ongoing, standards for the efficacy of treatments have yet to be developed. Current diagnostic criteria for cancer cachexia are primarily based on loss of body mass and muscle function. However, these criteria are rather limiting, and in time, when weight loss is noticeable, it may be too late for treatment. Consequently, biomarkers for cancer cachexia would be valuable adjuncts to current diagnostic criteria, and for assessing potential treatments. Using high throughput methods such as “omics approaches”, a plethora of potential biomarkers have been identified. This article reviews and summarizes current studies of biomarkers for cancer cachexia.

Selective antibody targeted delivery of α particle emitting actinium-225 to tumors has significant therapeutic potential. This work highlights the design and synthesis of a new bifunctional macrocyclic diazacrown ether chelator, H₂MacropaSqOEt, that can be conjugated to antibodies and forms stable complexes with actinium-225. The macrocyclic diazacrown ether chelator incorporates a linker comprised of a short polyethylene glycol fragment and a squaramide ester that allows selective reaction with lysine residues on antibodies to form stable vinylogous amide linkages. This new H₂MacropaSqOEt chelator was used to modify a monoclonal antibody, girentuximab (hG250), that binds to carbonic anhydrase IX, an enzyme that is overexpressed on the surface of cancers such as clear cell renal cell carcinoma. This new antibody conjugate (H₂MacropaSq-hG250) had an average chelator to antibody ratio of 4 : 1 and retained high affinity for carbonic anhydrase IX. H₂MacropaSq-hG250 was radiolabeled quantitatively with [²²⁵Ac]Ac^III within one minute at room temperature with micromolar concentrations of antibody and the radioactive complex is stable in human serum for >7 days. Evaluation of [²²⁵Ac]Ac(MacropaSq-hG250) in a mouse xenograft model, that overexpresses carbonic anhydrase IX, demonstrated a highly significant therapeutic response. It is likely that H₂MacropaSqOEt could be used to modify other antibodies providing a readily adaptable platform for other actinium-225 based therapeutics.

Background: Cachexia, a complex multi‐organ syndrome, shortens survival time of patients, particularly those with cancer. Many studies and clinical trials have been carried out to identify cachexia‐inducing factors and potential treatments for cancer cachexia over the last 20 years. Of these factors, some are promising targets for treatment in humans, owing to their expression profiles in patients. Several clinical interventions, which act on either cachexia‐inducing factors or tissues affected by cachexia, have been developed. Some have had positive effects in the treatment of cancer cachexia; however, the question remains whether these interventions reverse cancer cachexia and could be used as standard interventions for disease treatment. The aim of this review is to understand the basic mechanisms and factors that induce cancer cachexia and their efficacies in clinical trials, providing a better outlook for future studies of cancer cachexia.Methods: A systematic search was performed using PubMed and ClinicalTrials.gov databases for cachexia mediators and clinical trials.Results: Of all databases and peer‐reviewed facts considered, 256 papers and 35 clinical trials were included in this systematic review. Twenty‐one mediators were identified, and 17 clinical interventions were reported in these studies. Outcomes of these clinical trials were assessed on changes in overall survival, body weight, lean body mass, appetite, muscle strength, muscle function, quality of life, and cytokine levels.Conclusions: There is no current standard or successful intervention for treating cancer cachexia. Further research is needed to improve our understanding of initiators of cachexia to achieve successful outcomes in cachexia clinical trials.