Quantitative proteomics identifies NCOA4 as the cargo receptor mediating ferritinophagy

Autophagy, the process by which proteins and organelles are sequestered in double-membrane structures called autophagosomes and delivered to lysosomes for degradation, is critical in diseases such as cancer and neurodegeneration1,2. Much of our understanding of this process has emerged from analysis of bulk cytoplasmic autophagy, but our understanding of how specific cargo including organelles, proteins, or intracellular pathogens are targeted for selective autophagy is limited3. We employed quantitative proteomics to identify a cohort of novel and known autophagosome-enriched proteins, including cargo receptors. Like known cargo receptors, NCOA4 was highly enriched in autophagosomes, and associated with ATG8 proteins that recruit cargo-receptor complexes into autophagosomes. Unbiased identification of NCOA4-associated proteins revealed ferritin heavy and light chains, components of an iron-filled cage structure that protects cells from reactive iron species4 but is degraded via autophagy to release iron5,6 through an unknown mechanism. We found that delivery of ferritin to lysosomes required NCOA4, and an inability of NCOA4-deficient cells to degrade ferritin leads to decreased bioavailable intracellular iron. This work identifies NCOA4 as a selective cargo receptor for autophagic turnover of ferritin (ferritinophagy) critical for iron homeostasis and provides a resource for further dissection of autophagosomal cargo-receptor connectivity

Serine-arginine protein kinase 1 (SRPK1), a determinant of angiogenesis, is upregulated in prostate cancer and correlates with disease stage and invasion

Vascular endothelial growth factor (VEGF) undergoes alternative splicing to produce both proangiogenic and antiangiogenic isoforms. Preferential splicing of proangiogenic VEGF is determined by serine-arginine protein kinase 1 (SRPK1), which is upregulated in a number of cancers. In the present study, we aimed to investigate SRPK1 expression in prostate cancer (PCa) and its association with cancer progression. SRPK1 expression was assessed using immunohistochemistry of PCa tissue extracted from radical prostatectomy specimens of 110 patients. SRPK1 expression was significantly higher in tumour compared with benign tissue (p<0.00001) and correlated with higher pT stage (p=0.004), extracapsular extension (p=0.003) and extracapsular perineural invasion (p=0.008). Interestingly, the expression did not correlate with Gleason grade (p=0.21), suggesting that SRPK1 facilitates the development of a tumour microenvironment that favours growth and invasion (possibly through stimulating angiogenesis) while having little bearing on the morphology or function of the tumour cells themselves

Vascular endothelial growth factor-A165b restores normal glomerular water permeability in a diphtheria-toxin mouse model of glomerular injury

BACKGROUND/AIMS:Genetic cell ablation using the human diphtheria toxin receptor (hDTR) is a new strategy used for analysing cellular function. Diphtheria toxin (DT) is a cytotoxic protein that leaves mouse cells relatively unaffected, but upon binding to hDTR it ultimately leads to cell death. We used a podocyte-specific hDTR expressing (Pod-DTR) mouse to assess the anti-permeability and cyto-protective effects of the splice isoform vascular endothelial growth factor (VEGF-A165b). METHODS:The Pod-DTR mouse was crossed with a mouse that over-expressed VEGF-A165b specifically in the podocytes (Neph-VEGF-A165b). Wild type (WT), Pod-DTR, Neph-VEGF-A165b and Pod-DTR X Neph-VEGF-A165b mice were treated with several doses of DT (1, 5, 100, and 1,000 ng/g bodyweight). Urine was collected and the glomerular water permeability (LpA/Vi) was measured ex vivo after 14 days. Structural analysis and podocyte marker expression were also assessed. RESULTS: Pod-DTR mice developed an increased glomerular LpA/Vi 14 days after administration of DT (all doses), which was prevented when the mice over-expressed VEGF-A165b. No major structural abnormalities, podocyte ablation or albuminuria was observed in Pod-DTR mice, indicating this to be a mild model of podocyte disease. However, a change in expression and localisation of nephrin within the podocytes was observed, indicating disruption of the slit diaphragm in the Pod-DTR mice. This was prevented in the Pod-DTR X Neph-VEGF-A165b mice. CONCLUSION: Although only a mild model of podocyte injury, over-expression of the anti-permeability VEGF-A165b isoform in the podocytes of Pod-DTR mice had a protective effect. Therefore, this study further highlights the therapeutic potential of VEGF-A165b in glomerular disease

Failure to up-regulate VEGF165b in maternal plasma is a first trimester predictive marker for pre-eclampsia

Pre-eclampsia is a pregnancy-related condition characterized by hypertension, proteinuria and endothelial dysfunction. VEGF165b, formed by alternative splicing of VEGF (vascular endothelial growth factor) pre-mRNA, inhibits VEGF165-mediated vasodilation and angiogenesis, but has not been quantified in pregnancy. ELISAs were used to measure means±S.E.M. plasma VEGF165b, sEng (soluble endoglin) and sFlt-1 (soluble fms-like tyrosine kinase-1). At 12 weeks of gestation, the plasma VEGF165b concentration was significantly up-regulated in plasma from women who maintained normal blood pressure throughout their pregnancy (normotensive group, 4.90±1.6 ng/ml; P<0.01, as determined using a Mann-Whitney U test) compared with non-pregnant women (0.40±0.22 ng/ml). In contrast, in patients who later developed pre-eclampsia, VEGF165b levels were lower than in the normotensive group (0.467±0.209 ng/ml), but were no greater than non-pregnant women. At term, plasma VEGF165b concentrations were greater than normal in both pre-eclamptic (3.75±2.24 ng/ml) and normotensive (10.58 ng/ml±3.74 ng/ml; P>0.1 compared with pre-eclampsia) pregnancies. Patients with a lower than median plasma VEGF165b at 12 weeks had elevated sFlt-1 and sEng pre-delivery. Concentrations of sFlt-1 (1.20±0.07 and 1.27±0.18 ng/ml) and sEng (4.4±0.18 and 4.1±0.5 ng/ml) were similar at 12 weeks of gestation in the normotensive and pre-eclamptic groups respectively. Plasma VEGF165b levels were elevated in pregnancy, but this increase is delayed in women that subsequently develop pre-eclampsia. In conclusion, low VEGF165b may therefore be a clinically useful first trimester plasma marker for increased risk of pre-eclampsia

Noninvasive fractal biomarker of clock neurotransmitter disturbance in humans with dementia

Human motor activity has a robust, intrinsic fractal structure with similar patterns from minutes to hours. The fractal activity patterns appear to be physiologically important because the patterns persist under different environmental conditions but are significantly altered/reduced with aging and Alzheimer's disease (AD). Here, we report that dementia patients, known to have disrupted circadian rhythmicity, also have disrupted fractal activity patterns and that the disruption is more pronounced in patients with more amyloid plaques (a marker of AD severity). Moreover, the degree of fractal activity disruption is strongly associated with vasopressinergic and neurotensinergic neurons (two major circadian neurotransmitters) in postmortem suprachiasmatic nucleus (SCN), and can better predict changes of the two neurotransmitters than traditional circadian measures. These findings suggest that the SCN impacts human activity regulation at multiple time scales and that disrupted fractal activity may serve as a non-invasive biomarker of SCN neurodegeneration in dementia