Project description:Comparison between WT Stm1, deltaN terminal and control AP-MS. The pulldown was performed with 3 biological indipendent replicates.
Project description:A long-standing question in developmental and reproductive biology is when the mammalian embryo becomes sufficiently distinct from its oocyte precursor. Myriads of studies examined the messenger RNAs that change during the oocyte-to-embryo transition, whereas proteins have been much less studied, in spite of their greater vicinity to phenotype. In the present study we modified the widely used embryo culture medium KSOM (PMID 12470333, PMID 10859270) to make it apt for our application. We replaced the serum albumin with polyvinylpyrrolidone and also replaced the natural Arginine and Lysine with their “heavy” isotopic variants Arginine 13C 15N and Lysine 13C 15N. Fertilized oocytes were retrieved from oviducts of gonadotropin-primed B6C3F1 females mated to CD1 males, and cultured at 37 degrees Celsius under 5% CO2 in KSOM containing 0.3 mM Arginine 13C 15N and 0.2 mM Lysine 13C 15N, which are the regular concentrations of these two amino acids in KSOM medium (PMID 12470333; PMID 10859270). After 4 days of culture, the embryos of the isotopic group had undergone blastocyst formation just like the control embryos cultured in normal medium. Samples of approx. 500 “heavy”-labeled blastocysts were collected zona-free and subjected to mass spectrometric analysis. The median labeling rate was 83%, ranging from 0% in proteins that did not incorporate any Arginine 13C 15N and Lysine 13C 15N, to 100% in proteins that were completely labeled. Our study demonstrates that a commonly used, chemically defined medium can be adapted for Stable Isotope Labeling by/with Amino acids in Cell culture (SILAC) and combined with high-resolution mass spectrometry, in a preimplantation embryo setting. This allows to tackle long-standing questions in developmental and reproductive biology, such as the identification of putative maternal (0% labeled), putative embryonic (100% labeled) or shared proteins in live mammalian embryos.
Project description:Type IVa pili (T4aP) are versatile bacterial cell surface structures that undergo extension/adhesion/retraction cycles powered by the cell envelope-spanning T4aP machine. In this machine, a complex composed of four minor pilins and PilY1 primes T4aP extension and is also present at the pilus tip mediating adhesion. Similar to many other bacteria, Myxococcus xanthus contains multiple minor pilins/PilY1 sets, the function of which remains unknown.Here, we report that minor pilins and PilY1 of cluster_1 (PilY1.1) form calcium-responsive priming and tip complexes contingent on a non-canonical cytochrome c (TfcP) with an unusual His/Cys heme ligation. We provide evidence that TfcP is unlikely to participate in electron transport and has been repurposed to promote calcium binding by PilY1.1 at low calcium concentrations, thereby stabilising PilY1.1 and enabling its function in a broader range of calcium concentrations. These results identify a novel function of cytochromes c and illustrate how incorporating an accessory factor expands the environmental range under which the T4aP system functions.
Project description:Commercial human heart whole tissue lysates were analyzed with LC-MS/MS with an inclusion list of alternative sequences (Lau et al. bioRxiv 2019).
Project description:Targeted SILAC determination of the rate of synthesis of proteins involved in mitochondrial structure and ETC activity in CT26 control and IF1-ablated cell lines
Project description:Ubiquitination is a post-translational modification that signals multiple processes, including protein degradation, trafficking and DNA repair. Polyubiquitin accumulates globally during the oxidative stress response, and this has been mainly attributed to increased ubiquitin conjugation and perturbations in protein degradation. Here we show that the unconventional Lys 63 (K63)-linked polyubiquitin accumulates in the yeast Saccharomyces cerevisiae in a highly sensitive and regulated manner as a result of exposure to peroxides. We demonstrate that hydrogen peroxide inhibits the deubiquitinating enzyme Ubp2, leading to accumulation of K63 conjugates assembled by the Rad6 ubiquitin conjugase and the Bre1 ubiquitin ligase. Using linkage-specific isolation methods and stable isotope labeling by amino acids in cell culture (SILAC)–based quantitative proteomics, we identified >100 new K63-polyubiquitinated targets, which were substantially enriched in ribosomal proteins. Finally, we demonstrate that impairment of K63 ubiquitination during oxidative stress affects polysome stability and protein expression, rendering cells more sensitive to stress, and thereby reveal a new redox-regulatory role for this modification.
Project description:Skeletal muscle is known to adapt dynamically to changes in workload by regulatory processes of the phosphatidylinositide 3-kinase (PI3K)/Akt pathway. We performed a global quantitative phosphoproteomics analysis of contracting mouse C2 myotubes treated with insulin growth factor 1 (IGF-1) or LY294002 to activate or inhibit PI3K/Akt signaling, respectively. Among the significantly regulated phosphopeptides we identified the novel extended basophilic motif RxRxxp[S/T]xxp[S] to be enriched in the set of down-regulated phosphopeptides following inhibition of PI3K/Akt signaling. Using literature-based text mining we identified the kinases Akt, serum and glucocorticoid-regulated kinase 1 (SGK1) and p70S6 kinase to be potentially involved in the phosphorylation of the first serine in the RxRxxp[S/T]xxp[S] motif, whereas no kinase targeting the serine in the +3 position was revealed. In the signaling adapter protein filamin c (FLNc) we found this novel motif in immunoglobulin (Ig)-like domain 20 which is involved in various protein interactions. Through in vitro and in cellulo kinase assays we identified Akt and protein kinase C alpha as the responsible kinases phosphorylating FLNc in this motif at the first and the second serine, respectively.