Regulation of proteasome structure and function

Proteasomes are cylindrical particles made up of a stack of four heptameric rings. In animal cells the outer rings are made up of 7 different types of alpha subunits and the inner rings are composed of 7 out of 10 possible different beta subunits. Regulatory complexes can bind to the ends of the cylinder.We have investigated aspects of the assembly, activity and subunit composition of core proteasome particles and 26S proteasomes, the localization of proteasome subpopulations, and the possible role of phosphorylation in determining proteasome localization, activities and association with regulatory components.

Corneal nerve structure and function as markers of diabetic neuropathy

Diabetic neuropathy is a significant clinical problem that currently has no effective therapy, and in advanced cases, leads to foot ulceration and lower limb amputation. The accurate detection, characterisation and quantification of this condition are important in order to define at-risk patients, anticipate deterioration, monitor progression and assess new therapies. This thesis evaluates novel corneal methods of assessing diabetic neuropathy. Over the past several years two new non-invasive corneal markers have emerged, and in cross-sectional studies have demonstrated their ability to stratify the severity of this disease. Corneal confocal microscopy (CCM) allows quantification of corneal nerve parameters and non-contact corneal aesthesiometry (NCCA), the presumed functional correlate of corneal structure, assesses the sensitivity of the cornea. Both these techniques are quick to perform, produce little or no discomfort for the patient, and with automatic analysis paradigms developed, are suitable for clinical settings. Each has advantages and disadvantages over established techniques for assessing diabetic neuropathy. New information is presented regarding measurement bias of CCM images, and a unique sampling paradigm and associated accuracy determination method of combinations is described. A novel high-speed corneal nerve mapping procedure has been developed and application of this procedure in individuals with neuropathy has revealed regions of sub-basal nerve plexus that dictate further evaluation, as they appear to show earlier signs of damage than the central region of the cornea that has to date been examined. The discriminative capacity of corneal sensitivity measured by NCCA is revealed to have reasonable potential as a marker of diabetic neuropathy. Application of these new corneal markers for longitudinal evaluation of diabetic neuropathy has the potential to reduce dependence on more invasive, costly, and time-consuming assessments, such as skin biopsy.

Human proximal tubule epithelial cells modulate autologous dendritic cell function

Background We have previously demonstrated that human kidney proximal tubule epithelial cells (PTEC) are able to modulate autologous T and B lymphocyte responses. It is well established that dendritic cells (DC) are responsible for the initiation and direction of adaptive immune responses and that these cells occur in the renal interstitium in close apposition to PTEC under inflammatory disease settings. However, there is no information regarding the interaction of PTEC with DC in an autologous human context. Methods Human monocytes were differentiated into monocyte-derived DC (MoDC) in the absence or presence of primary autologous activated PTEC and matured with polyinosinic:polycytidylic acid [poly(I:C)], while purified, pre-formed myeloid blood DC (CD1c+ BDC) were cultured with autologous activated PTEC in the absence or presence of poly(I:C) stimulation. DC responses were monitored by surface antigen expression, cytokine secretion, antigen uptake capacity and allogeneic T-cell-stimulatory ability. Results The presence of autologous activated PTEC inhibited the differentiation of monocytes to MoDC. Furthermore, MoDC differentiated in the presence of PTEC displayed an immature surface phenotype, efficient phagocytic capacity and, upon poly(I:C) stimulation, secreted low levels of pro-inflammatory cytokine interleukin (IL)-12p70, high levels of anti-inflammatory cytokine IL-10 and induced weak Th1 responses. Similarly, pre-formed CD1c+ BDC matured in the presence of PTEC exhibited an immature tolerogenic surface phenotype, strong endocytic and phagocytic ability and stimulated significantly attenuated T-cell proliferative responses. Conclusions Our data suggest that activated PTEC regulate human autologous immunity via complex interactions with DC. The ability of PTEC to modulate autologous DC function has important implications for the dampening of pro-inflammatory immune responses within the tubulointerstitium in renal injuries. Further dissection of the mechanisms of PTEC modulation of autologous immune responses may offer targets for therapeutic intervention in renal medicine.

Delta opioid-receptor function in the dorsal striatum plays a role in high levels of ethanol consumption in rats

Binge-like patterns of excessive drinking during young adulthood increase the propensity for alcohol use disorders (AUDs) later in adult life; however, the mechanisms that drive this are not completely understood. Previous studies showed that the δ-opioid peptide receptor (DOP-R) is dynamically regulated by exposure to ethanol and that the DOP-R plays a role in ethanol-mediated behaviors. The aim of this study was to determine the role of the DOP-R in high ethanol consumption from young adulthood through to late adulthood by measuring DOP-R-mediated [(35)S]GTPγS binding in brain membranes and DOP-R-mediated analgesia using a rat model of high ethanol consumption in Long Evans rats. We show that DOP-R activity in the dorsal striatum and DOP-R-mediated analgesia changes during development, being highest during early adulthood and reduced in late adulthood. Intermittent access to ethanol but not continuous ethanol or water from young adulthood leads to an increase in DOP-R activity in the dorsal striatum and DOP-R-mediated analgesia into late adulthood. Multiple microinfusions of naltrindole into the dorsal striatum or multiple systemic administration of naltrindole reduces ethanol consumption, and following termination of treatment, DOP-R activity in the dorsal striatum is attenuated. These findings suggest that DOP-R activity in the dorsal striatum plays a role in high levels of ethanol consumption and suggest that targeting the DOP-R is an alternative strategy for the treatment of AUDs.

Exercise for health : a randomized, controlled trial evaluating impact of a pragmatic, translational exercise intervention on quality of life, function and treatment-related side effects following breast cancer

Purpose Exercise for Health was a randomized, controlled trial designed to evaluate two modes of delivering (face-to-face [FtF] and over-the-telephone [Tel]) an 8-month translational exercise intervention, commencing 6-weeks post-breast cancer surgery (PS). Methods Outcomes included quality of life (QoL), function (fitness and upper-body) and treatment-related side effects (fatigue, lymphoedema, body mass index, menopausal symptoms, anxiety, depression and pain). Generalised estimating equation modelling determined time (baseline [5-weeks PS], mid-intervention [6-months PS], post-intervention [12-months PS]), group (FtF, Tel, Usual Care [UC]) and time-by-group effects. 194 women representative of the breast cancer population were randomised to the FtF (n=67), Tel (n=67) and UC (n=60) groups. Results: There were significant (p<0.05) interaction effects on QoL, fitness and fatigue, with differences being observed between the treatment groups and the UC group. Trends observed for the treatment groups were similar. The treatment groups reported improved QoL, fitness and fatigue over time and changes observed between baseline and post-intervention were clinically relevant. In contrast, the UC group experienced no change, or worsening QoL, fitness and fatigue, mid-intervention. Although improvements in the UC group occurred by 12-months post-surgery, the change did not meet the clinically relevant threshold. There were no differences in other treatment-related side-effects between groups. Conclusion This translational intervention trial, delivered either face-to-face or over-the-telephone, supports exercise as a form of adjuvant breast cancer therapy that can prevent declines in fitness and function during treatment and optimise recovery post-treatment.

Evidence for a dual function of EphB4 as tumor promoter and suppressor regulated by the absence or presence of the ephrin-B2 ligand

Overexpression of the receptor tyrosine kinase EphB4 is common in epithelial cancers and linked to tumor progression by promoting angiogenesis, increasing survival and facilitating invasion and migration. However, other studies have reported loss of EphB4 suggesting a tumor suppressor function in some cancers. These opposing roles may be regulated by (i) the presence of the primary ligand ephrin-B2 that regulates pathways involved in tumor suppression or (ii) the absence of ephrin-B2 that allows EphB4 signaling via ligand-independent pathways that contribute to tumor promotion. To explore this theory, EphB4 was overexpressed in the prostate cancer cell line 22Rv1 and the mammary epithelial cell line MCF-10A. Overexpressed EphB4 localized to lipid-rich regions of the plasma membrane and confirmed to be ligand-responsive as demonstrated by increased phosphorylation of ERK1/2 and internalization. EphB4 overexpressing cells demonstrated enhanced anchorage-independent growth, migration and invasion, all characteristics associated with an aggressive phenotype, and therefore supporting the hypothesis that overexpressed EphB4 facilitates tumor promotion. Importantly, these effects were reversed in the presence of ephrin-B2 which led to a reduction in EphB4 protein levels, demonstrating that ligand-dependent signaling is tumor suppressive. Furthermore, extended ligand stimulation caused a significant decrease in proliferation that correlated with a rise in caspase-3/7 and -8 activities. Together, these results demonstrate that overexpression of EphB4 confers a transformed phenotype in the case of MCF-10A cells and an increased metastatic phenotype in the case of 22Rv1 cancer cells and that both phenotypes can be restrained by stimulation with ephrin-B2, in part by reducing EphB4 levels.

The post-illumination pupil response of melanopsin expressing intrinsically photosensitive retinal ganglion cells in diabetes

Purpose: This study investigates the clinical utility of the melanopsin expressing intrinsically photosensitive retinal ganglion cell (ipRGC) controlled post-illumination pupil response (PIPR) as a novel technique for documenting inner retinal function in patients with Type II diabetes without diabetic retinopathy. Methods: The post-illumination pupil response (PIPR) was measured in seven patients with Type II diabetes, normal retinal nerve fiber thickness and no diabetic retinopathy. A 488 nm and 610 nm, 7.15º diameter stimulus was presented in Maxwellian view to the right eye and the left consensual pupil light reflex was recorded. Results: The group data for the blue PIPR (488 nm) identified a trend of reduced ipRGC function in patients with diabetes with no retinopathy. The transient pupil constriction was lower on average in the diabetic group. The relationship between duration of diabetes and the blue PIPR amplitude was linear, suggesting that ipRGC function decreases with increasing diabetes duration. Conclusion: This is the first report to show that the ipRGC controlled post-illumination pupil response may have clinical applications as a non-invasive technique for determining progression of inner neuroretinal changes in patients with diabetes before they are ophthalmoscopically or anatomically evident. The lower transient pupil constriction amplitude indicates that outer retinal photoreceptor inputs to the pupil light reflex may also be affected in diabetes.

Insights into the role and function of L2, the minor capsid protein of papillomaviruses

Human papillomaviruses (HPV) are responsible for the most common human sexually transmitted viral infections, and high-risk types are responsible for causing cervical and other cancers. The minor capsid protein L2 of HPV plays important roles in virus entry into cells, localisation of viral components to the nucleus, in DNA binding, capsid formation and stability. It also elicits antibodies that are more cross-reactive between HPV types than does the major capsid protein L1, making it an attractive potential target for new-generation, more broadly protective subunit vaccines against HPV infections. However, its low abundance in natural capsids-12-72 molecules per 360 copies of L1-limits its immunogenicity. This review will explore the biological roles of the protein, and prospects for its use in new vaccines. © 2009 Springer-Verlag.