Systemic amyloidosis is a serious disease which is caused when normal circulating proteins misfold and aggregate extracellularly as insoluble fibrillary deposits throughout the body. This commonly ...results in cardiac, renal and neurological damage. The tissue target, progression and outcome of the disease depends on the type of protein forming the fibril deposit, and its correct identification is central to determining therapy. Proteomics is now used routinely in our centre to type amyloid; over the past 7 years we have examined over 2000 clinical samples. Proteomics results are linked directly to our patient database using a simple algorithm to automatically highlight the most likely amyloidogenic protein. Whilst the approach has proved very successful, we have encountered a number of challenges, including poor sample recovery, limited enzymatic digestion, the presence of multiple amyloidogenic proteins and the identification of pathogenic variants. Our proteomics procedures and approaches to resolving difficult issues are outlined.
The emergence of a polybasic cleavage motif for the protease furin in SARS-CoV-2 spike has been established as a major factor for human viral transmission. The region N-terminal to that motif is ...extensively mutated in variants of concern (VOCs). Besides furin, spikes from these variants appear to rely on other proteases for maturation, including TMPRSS2. Glycans near the cleavage site have raised questions about proteolytic processing and the consequences of variant-borne mutations. Here, we identify that sialic acid-containing O-linked glycans on Thr678 of SARS-CoV-2 spike influence furin and TMPRSS2 cleavage and posit O-linked glycosylation as a likely driving force for the emergence of VOC mutations. We provide direct evidence that the glycosyltransferase GalNAc-T1 primes glycosylation at Thr678 in the living cell, an event that is suppressed by mutations in the VOCs Alpha, Delta, and Omicron. We found that the sole incorporation of N-acetylgalactosamine did not impact furin activity in synthetic O-glycopeptides, but the presence of sialic acid reduced the furin rate by up to 65%. Similarly, O-glycosylation with a sialylated trisaccharide had a negative impact on TMPRSS2 cleavage. With a chemistry-centered approach, we substantiate O-glycosylation as a major determinant of spike maturation and propose disruption of O-glycosylation as a substantial driving force for VOC evolution.
Proteomics is becoming the de facto gold standard for identifying amyloid proteins and is now used routinely in a number of centres. The technique is compound class independent and offers the added ...ability to identify variant and modified proteins. We re-examined proteomics results from a number of formalin-fixed paraffin-embedded amyloid samples, which were positive for transthyretin (TTR) by immunohistochemistry and proteomics, using the UniProt human protein database modified to include TTR variants. The amyloidogenic variant, V122I TTR, was incorrectly identified in 26/27 wild-type and non-V122I variant samples due to its close mass spectral similarity with the methyl lysine-modified WT peptide 126K
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105-127 (p.146 K
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125-147) generated during formalin fixation. Similarly, the methyl lysine peptide, 50K
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43-59, from immunoglobulin lambda light chain constant region was also misidentified as arising from a rare myeloma-derived lambda variant V49I. These processing-derived modifications are not present in fresh cardiac tissue, non-fixed fat nor serum and do not materially affect the identification of amyloid proteins. They could result in the incorrect assignment of a variant, and this may have consequences for the immediate family who will require genetic counselling and potentially early clinical intervention. As proteomics becomes a routine clinical test for amyloidosis, it becomes important to be aware of potentially confounding issues such as formalin-mediated lysine methylation, and how these may influence diagnosis and possibly treatment.
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Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Abstract Introduction Few studies have been carried out to investigate whether distinct areas of full term placenta express different amounts of markers involved in the placental haemostasis and ...angiogenesis. A possible relationship between the expression of genes involved in the haemostasis and angiogenesis of human placenta has not been investigated. Materials and methods Twenty-eight fresh human placentas (35–41 weeks of gestation) from uneventful pregnancies were dissected with two different methods. Quantitative mRNA expression of the tissue factor (TF), TF pathway inhibitor (TFPI), TFPI-2, plasminogen activator inhibitor (PAI-2), annexin V (Anx V), vascular endothelial growth factor (VEGF), and thrombomodulin (TM) genes was evaluated by quantitative real time PCR system. Histology of each sample was graded. Results Gene expression of all the considered markers was not significantly different in each area, using both the different methods of dissection. A significant correlation ( p < 0.05) was found between the expression of TF and TFPI-2. TF and TFPI-2 were significantly ( p < 0.05) associated with VEGF, whereas a stronger association ( p < 0.01) was found between TFPI and TFPI-2. TFPI and TFPI-2 were strongly associated with PAI-2 expression ( p < 0.01). Conclusions In placentas with central cord insertion, gene expression is not dependent on the method of sampling site. A significant relationship between haemostasis and angiogenesis in at term placentas was shown.
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