Phototrophic chromalveolates possess plastids surrounded by either 3 or 4 membranes, revealing their secondary endosymbiotic origin from an engulfed eukaryotic alga. In cryptophytes, a member of the chromalveolates, the organelle is embedded within a designated region of the host's rough endoplasmic reticulum (RER). Its eukaryotic compartments other than the plastid were reduced to the mere remains of its former cytosol, the periplastid compartment (PPC, PP space), and its nucleus, the nucleomorph, separated from the RER by its former plasma membrane, the periplast membrane (PPM). In the nucleomorph genome of the cryptophyte Guillardia theta, we identified several genes sharing homology with components of the ER-associated degradation (ERAD) machinery of yeast and higher eukaryotes, namely ORF201 and ORF477, homologs of membrane-bound proteins, Der1p (Degradation in the ER protein 1) and the RING-finger ubiquitin ligase Hrd1, and a truncated version of Udf1, a cofactor of Cdc48, a lumenal ATPase. Exemplarily, studies on the Der1-homolog ORF201 showed that this protein partially rescued a yeast deletion mutant, indicating the existence of a functional PPC-specific ERAD-like system in cryptophytes. With the noninvestigated exception of haptophytes a phylogenetically and mechanistically related system is apparently present in all chromalveolates with 4 membrane-bound plastids because amongst others, PPC-specific Derlins (Der1-like proteins), CDC48 and its cofactor Ufd1 were identified in the nuclear genomes of diatoms and apicomplexa. These proteins are equipped with the required topogenic signals to direct them into the periplastid compartment of their secondary symbionts. Based on our findings, we suggest that all chromalveolates with 4 membrane-bound plastids express an ERAD-derived machinery in the PPM of their secondary plastid, coexisting physically and systematically adjacent to the host's own ERAD system. We propose herewith that this system was functionally adapted to mediate transport of nucleus-encoded PPC/plastid preproteins from the RER into the periplastid space.

Context/ObjectiveEpidemiological studies have demonstrated that women have a significantly better prognosis in chronic renal diseases compared to men. This suggests critical influences of gender hormones on glomerular structure and function. We examined potential direct protective effects of estradiol on podocytes.MethodsExpression of estrogen receptor alpha (ERα) was examined in podocytes in vitro and in vivo. Receptor localization was shown using Western blot of separated nuclear and cytoplasmatic protein fractions. Podocytes were treated with Puromycin aminonucleoside (PAN, apoptosis induction), estradiol, or both in combination. Apoptotic cells were detected with Hoechst nuclear staining and Annexin-FITC flow cytometry. To visualize mitochondrial membrane potential depolarization as an indicator for apoptosis, cells were stained with tetramethyl rhodamine methylester (TMRM). Estradiol-induced phosphorylation of ERK1/2 and p38 MAPK was examined by Western blot. Glomeruli of ERα knock-out mice and wild-type controls were analysed by histomorphometry and immunohistochemistry.ResultsERα was consistently expressed in human and murine podocytes. Estradiol stimulated ERα protein expression, reduced PAN-induced apoptosis in vitro by 26.5±24.6% or 56.6±5.9% (flow cytometry or Hoechst-staining, respectively; both p<0.05), and restored PAN-induced mitochondrial membrane potential depolarization. Estradiol enhanced ERK1/2 phosphorylation. In ERα knockout mice, podocyte number was reduced compared to controls (female/male: 80/86 vs. 132/135 podocytes per glomerulus, p<0.05). Podocyte volume was enhanced in ERα knockout mice (female/male: 429/371 µm3 vs. 264/223 µm3 in controls, p<0.05). Tgfβ1 and collagen type IV expression were increased in knockout mice, indicating glomerular damage.ConclusionsPodocytes express ERα, whose activation leads to a significant protection against experimentally induced apoptosis. Possible underlying mechanisms include stabilization of mitochondrial membrane potential and activation of MAPK signalling. Characteristic morphological changes indicating glomerulopathy in ERα knock-out mice support the in vivo relevance of the ERα for podocyte viability and function. Thus, our findings provide a novel model for the protective influence of female gender on chronic glomerular diseases.

Large vessel vasculitis can be visualized by 18F-FDG positron emission tomography (PET). However, the diagnostic value of 18F-FDG PET is yet to be determined. We therefore performed a study to evaluate this technique for the diagnosis of giant cell arteritis (GCA) and Takayasu arteritis (TA). Patients with GCA or TA, who fulfilled the American College of Rheumatology (ACR) criteria and also had a pathologic PET scan in clinical routine, were selected. These PET scans, as well as PET scans obtained from age- and sex-matched control patients, were independently re-evaluated by two experienced nuclear medicine experts. PET scans of 20 patients (17 GCA, 3 TA) and 20 controls were evaluated. In 85% of the examinations, both observers agreed on the diagnosis or exclusion of vasculitis. Specificity was calculated with 80% and sensitivity with 65%, yielding an overall diagnostic accuracy of 72%. The mean maximum standardized uptake values (SUVmax) of the subclavian region was significantly higher in vasculitis than in control patients (2.77 ± 1.02 vs 2.09 ± 0.64; difference 0.69; CI(95%): 0.14-1.24, p = 0.0161). SUVmax of the iliacal regions did not differ significantly. Receiver- operating characteristics (ROC) analysis revealed the highest sensitivity of 90% (CI(95%): 68-99%) and specificity of 45% (CI(95%): 23-69%) for a SUVmax cut-off point of 1.78 (AUC 0.72, (CI(95%): 0.56-0.86). PET findings are reproducible and independent of the observer. The low sensitivity and specificity indicate that enhanced vascular uptake might be overrated if clinical details are suggestive for vasculitis. Therefore, the diagnosis of large vessel vasculitis should not be based on PET findings only.

Blue light modulates many processes in plants and plant cells. It influences global and long-term responses, such as seedling development and phototropism, and induces short-term adaptations like stomatal opening and chloroplast movement. Three genes were identified as important for the latter process, namely PHOT1, PHOT2 and CHUP1. The former two phototropin blue light receptors act in perception of the blue light signal. The protein CHUP1 is localised to the outer envelope membrane of chloroplasts and is involved in chloroplast movement. To explore whether short-term reactions required for chloroplast movement are under transcriptional control, we analysed the transcriptome in wild-type Arabidopsis thaliana, phot1, phot2 and chup1 with different blue light treatments for 5 or 30 min. Blue light-induced changes in transcription depended on illumination time and intensity. Illumination with 100 μmol·m(-2) · s(-1) blue light induced down-regulation of several genes and might point to cascades that could be important for sensing low levels of blue light. Analysis of the transcriptome of the mutants in response to the different light regimes suggests that the transcriptional response to blue light in the wild-type can be attributed to phot1 rather than phot2, suggesting that blue light-induced alteration of expression is a function of phot1. In contrast, the blue light response at the transcriptional level of chup1 plants was unique, and confirmed the higher light sensitivity of this mutant.