Project description:Acetylation of α-tubulin at conserved lysine 40 (K40) amino acid residue regulates microtubule dynamics and controls a wide range of cellular activities. Dysregulated microtubule dynamics characterised by differential α-tubulin acetylation is a hallmark of cancer, neurodegeneration and other complex disorders. Hence, accurate quantitation of α-tubulin acetylation is required in human disease and animal model studies. We developed a novel antibody-free proteomics assay to measure α-tubulin acetylation targeting protease AspN-generated peptides harbouring K40 site. Using the synthetic unmodified and acetylated stable isotope labelled peptides DKTIGGG and DKTIGGGD, we demonstrate assay linearity across 4 log magnitude and reproducibility of <10% coefficient of variation . The assay accuracy was validated by titration of 10% to 80% mixture of acetylated/non-acetylated α-tubulin peptides in the background of human olfactory neurosphere-derived stem (ONS) cell matrix. Furthermore, in agreement with antibody-based high content microscopy analysis, the targeted proteomics assay reported an induction of α-tubulin K40 acetylation upon Trichostatin A stimulation of ONS cells. Independently, we found 35.99% and 16.11% α-tubulin acetylation for mouse spinal cord and brain homogenate tissue, respectively, as measured by our assay. In conclusion, this simple, antibody-free proteomics assay enables quantitation of α-tubulin acetylation, and is applicable across various fields of biology and medicine.
Project description:Tubulin detyrosination-tyrosination cycle regulates the stability of microtubules. Thus far described on α-tubulins, the tyrosination level is maintained by a single tubulin-tyrosine ligase (TTL). However, the precise dynamics and tubulin isoforms which undergo (de)tyrosination in neurons are unknown. Here, we exploit the substrate promiscuity of the TTL to introduce an O-propargyl-L-tyrosine in cancer cell lines and neurons. Mass spectrometry-based chemical proteomics in neuroblastoma cells using the O-propargyl-L-tyrosine probe revealed previously discussed tyrosination of TUBA4A, MAPRE1, and other non-tubulin proteins. This finding was further corroborated in differentiating neurons. We present the method for tubulin tyrosination profiling in living cells. Our results show that detyrosination-tyrosination is not restricted to α-tubulins with coded C-terminal tyrosine and is thus involved in fine-tuning of the tubulin and non-tubulin proteins during neuronal differentiation.
Project description:Microtubules (MTs) are built from alpha/beta-tubulin dimers and used as tracks by kinesin and dynein motors to transport a variety of cargos, such as mRNAs, proteins, and organelles, within the cell. Tubulins are subjected to several post-translational modifications (PTMs). Glutamylation is one of them, and it is responsible for adding one or more glutamic acid residues as branched peptide chains to the C-terminal tails of both alpha- and beta-tubulin. However, very little is known about the specific modifications found on the different tubulin isoforms in vivo and the role of these PTMs in cargo transport along MTs in vivo. In this study, we found that in Drosophila, glutamylation of the alpha-tubulin isoforms occurs specifically on the C-terminal ends of TBA1 and TBA3 in the ovaries. In contrast, the ovarian isoform TBA4 is not glutamylated. The C-terminal ends of TBA1 and TBA3 are glutamylated at several glutamyl side chains in various combinations. Drosophila TTLL5 is required for the mono- and polyglutamylation of ovarian TBA1 and 3. Furthermore, glutamylation of the alpha-tubulin is essential for the efficient localization of Staufen/osk mRNA and to give directionality to the fast ooplasmic streaming, two processes known to depend on kinesin mediated processes during oogenesis. In the nervous system, the kinesin-dependent neuronal transport of mitochondria also depends on TTLL5. Additionally, alpha-tubulin glutamylation affects the pausing of the transport of individual mitochondria in the axons. Our results demonstrate the in vivo role of TTLL5 in differential glutamylation of alpha-tubulin isoforms and point to the in vivo importance of alpha-tubulin glutamylation for kinesin-dependent processes.
Project description:PARP7 (TiPARP), a mono (ADP-ribosyl) transferase (MART) was found to target α-tubulin proteins in ovarian cancer cells, enhancing their growth and migration. RBN-2397 is a potent inhibitor that selectively acts on PARP7. Here, we show that RBN-2397 treatment leads to the stabilization of microtubules in ovarian cancer cells, namely α-tubulin, mimicking what was previously observed with PARP7 knockdown. When treated with RBN-2397, we observe a decrease in growth and migration of ovarian cancer cells and, interestingly, the effect is intensified upon adding the microtubule stabilizing chemotherapeutic agent, paclitaxel. Mutating the site of α-tubulin MARylation by PARP7 similarly results in α-tubulin stabilization and decreased cell migration in the presence of paclitaxel when the tubulin network is further stabilized. In sum, we demonstrate that PARP7 inhibition decreases α-tubulin MARylation resulting in its stabilization, and ultimately leading to decreased ovarian cancer cell proliferation and migration. Finally, we show that combining PARP7 inhibitor and paclitaxel results in a more robust inhibition of aggressive ovarian cancer phenotypes. Collectively, this study highlights the potential of targeting PARP7 in combination with established chemotherapeutic agents to enhance treatment efficacy for ovarian cancer.
Project description:12 wild-type C57BL/6 (B6) mice were divided into 4 groups: control group, IFN-α group, LPS group, and IFN-α+ LPS group, every group contained 3 mice (n=3). IFN-α was administrated i.p. to IFN-α group and IFN-α+ LPS group once daily (QD) for 7 days at a medium dose of 105units/kg weight, PBS was administrated i.p. to control group and LPS group QD for 7 days at the same volume. LPS group and IFN-α+ LPS group were injected i.v. with 10 μg LPS for one mouse on the 8th day. Control group and IFN-α group were injected i.v. with PBS at the same volume. 6 h later, mice were sacrificed to harvest spleens for protein microarray experiment. Mouse Cytokine Antibody Array 3(62) was purchased from Ray Biotech, Norcross GA, US. Protein microarray of murine cytokines expression. Spleens from 12 mice (4 group) were treated as indicated in the summary. Equal amount total protein from each spleen was pooled prior to gene expression analysis.