Tazarotene-induced gene 1 inhibits prostaglandin E2-stimulated HCT116 colon cancer cell growth

Remodeling the immune microenvironment for gastric cancer therapy through antagonism of prostaglandin E2 receptor 4

Gastric cancer is highly prevalent among digestive tract tumors. Due to the intricate nature of the gastric cancer immune microenvironment, there is currently no effective treatment available for advanced gastric cancer. However, there is promising potential for immunotherapy targeting the prostaglandin E2 receptor subtype 4 (EP4) in gastric cancer. In our previous study, we identified a novel small molecule EP4 receptor antagonist called YY001. Treatment with YY001 alone demonstrated a significant reduction in gastric cancer growth and inhibited tumor metastasis to the lungs in a mouse model. Furthermore, administration of YY001 stimulated a robust immune response within the tumor microenvironment, characterized by increased infiltration of antigen-presenting cells, T cells, and M1 macrophages. Additionally, our research revealed that YY001 exhibited remarkable synergistic effects when combined with the PD-1 antibody and the clinically targeted drug apatinib, rather than fluorouracil. These findings suggest that YY001 holds great promise as a potential therapeutic strategy for gastric cancer, whether used as a standalone treatment or in combination with other drugs.

Synthesis and Biological Evaluation of Some New 3-Aryl-2-thioxo-2,3-dihydroquinazolin-4(1H)-ones and 3-Aryl-2-(benzylthio)quinazolin-4(3H)-ones as Antioxidants; COX-2, LDHA, α-Glucosidase and α-Amylase Inhibitors; and Anti-Colon Carcinoma and Apoptosis-Inducing Agents

Oxidative stress, COX-2, LDHA and hyperglycemia are interlinked contributing pathways in the etiology, progression and metastasis of colon cancer. Additionally, dysregulated apoptosis in cells with genetic alternations leads to their progression in malignant transformation. Therefore, quinazolinones 3a-3h and 5a-5h were synthesized and evaluated as antioxidants, enzymes inhibitors and cytotoxic agents against LoVo and HCT-116 cells. Moreover, the most active cytotoxic derivatives were evaluated as apoptosis inducers. The results indicated that 3a, 3g and 5a were efficiently scavenged DPPH radicals with lowered IC50 values (mM) ranging from 0.165 ± 0.0057 to 0.191 ± 0.0099, as compared to 0.245 ± 0.0257 by BHT. Derivatives 3h, 5a and 5h were recognized as more potent dual inhibitors than quercetin against α-amylase and α-glucosidase, in addition to 3a, 3c, 3f and 5b-5f against α-amylase. Although none of the compounds demonstrated a higher efficiency than the reference inhibitors against COX-2 and LDHA, 3a and 3g were identified as the most active derivatives. Molecular docking studies were used to elucidate the binding affinities and binding interactions between the inhibitors and their target proteins. Compounds 3a and 3f showed cytotoxic activities, with IC50 values (µM) of 294.32 ± 8.41 and 383.5 ± 8.99 (LoVo), as well as 298.05 ± 13.26 and 323.59 ± 3.00 (HCT-116). The cytotoxicity mechanism of 3a and 3f could be attributed to the modulation of apoptosis regulators (Bax and Bcl-2), the activation of intrinsic and extrinsic apoptosis pathways via the upregulation of initiator caspases-8 and -9 as well as executioner caspase-3, and the arrest of LoVo and HCT-116 cell cycles in the G2/M and G1 phases, respectively. Lastly, the physicochemical, medicinal chemistry and ADMET properties of all compounds were predicted.

Tazarotene-induced gene 1 interacts with Polo-like kinase 2 and inhibits cell proliferation in HCT116 colorectal cancer cells

Tazarotene-induced gene 1 (TIG1) is considered to be a tumor suppressor gene that is highly expressed in normal or well-differentiated colon tissues, while downregulation of TIG1 expression occurs in poorly differentiated colorectal cancer (CRC) tissues. However, it is still unclear how TIG1 regulates the tumorigenesis of CRC. Polo-like kinases (Plks) are believed to play an important role in regulating the cell cycle. The performance of PLK2 in CRC is negatively correlated with the differentiation status of CRC tissues. Here, we found that PLK2 can induce the growth of CRC cells and that TIG1 can prevent PLK2 from promoting the proliferation of CRC cells. We also found that the expression of PLK2 in CRC cells was associated with low levels of Fbxw7 protein and increased expression of cyclin E1. When TIG1 was coexpressed with PLK2, the changes in Fbxw7/cyclin E1 levels induced by PLK2 were reversed. In contrast, silencing TIG1 promoted the proliferation of CRC, and when PLK2 was also silenced, the proliferation of CRC cells induced by TIG1 silencing was significantly inhibited. The above research results suggest that TIG1 can regulate the tumorigenesis of CRC by regulating the activity of PLK2.

Targeting GRK5 for Treating Chronic Degenerative Diseases

G protein-coupled receptors (GPCRs) are the largest family of cell-surface receptors and they are responsible for the transduction of extracellular signals, regulating almost all aspects of mammalian physiology. These receptors are specifically regulated by a family of serine/threonine kinases, called GPCR kinases (GRKs). Given the biological role of GPCRs, it is not surprising that GRKs are also involved in several pathophysiological processes. Particular importance is emerging for GRK5, which is a multifunctional protein, expressed in different cell types, and it has been found located in single or multiple subcellular compartments. For instance, when anchored to the plasma membrane, GRK5 exerts its canonical function, regulating GPCRs. However, under certain conditions (e.g., pro-hypertrophic stimuli), GRK5 translocates to the nucleus of cells where it can interact with non-GPCR-related proteins as well as DNA itself to promote “non-canonical” signaling, including gene transcription. Importantly, due to these actions, several studies have demonstrated that GRK5 has a pivotal role in the pathogenesis of chronic-degenerative disorders. This is true in the cardiac cells, tumor cells, and neurons. For this reason, in this review article, we will inform the readers of the most recent evidence that supports the importance of targeting GRK5 to prevent the development or progression of cancer, cardiovascular, and neurological diseases.

Synthesis and biological evaluation of new 3(2H)-pyridazinone derivatives as non-toxic anti-proliferative compounds against human colon carcinoma HCT116 cells

Novel 3(2H)-pyridazinone derivatives were designed, synthesised in satisfactory yields and evaluated in different experimental assays to assess their preliminary toxicity in vivo and anti-proliferative effects against HCT116 cell lines in vitro. Artemia salina lethality test provided LC50 values >100 µg/mL for all compounds. Successive assays revealed that some compounds were endowed with a promising anti-proliferative effect against HCT116 cells, alone or stimulated by serotonin as a pro-inflammatory factor in order to mimick an inflamed model in vivo of cancer cell microenvironment. Moreover, the kinurenic acid level after treatment with these newly synthesised compounds was monitored as a marker of anti-proliferation in colon carcinoma models. The IC50 values obtained for the best-in-class compounds were comparable to that of daunorubicin as a reference drug. Conversely, these compounds were not able to counteract the spontaneous migration of human cancer HCT116 cell line in the wound healing paradigm.

Biopotential of Bersama abyssinica Fresen Stem Bark Extracts: UHPLC Profiles, Antioxidant, Enzyme Inhibitory, and Antiproliferative Propensities

In this study, ethyl acetate, methanol, and water extracts of Bersama abyssinica (Melianthaceae) stem bark were screened for enzyme inhibitory and antioxidant properties. The water extract possessed the highest concentration of phenols (230.83 mg gallic acid equivalent/g extract), while the methanol extract was rich in flavonoids (75.82 mg rutin equivalent/g extract), and the ethyl acetate extract possessed the highest amount of saponins (97.37 mg quillaja equivalent/g). The aim of this study was to investigate the antiproliferative effects against the human colon cancer HCT116 cell line challenged with serotonin (5-HT) as a stimulating-proliferation factor. The level of HCT116 cell-deriving pool of kynurenic acid (KA) was also assessed. The UHPLC results confirmed the presence of 58, 68, and 63 compounds in the ethyl acetate, methanol, and water extracts, respectively. Mangiferin, vitexin and its isomer isovitexin were tentatively identified in all extracts and KA (m/z 190.05042 [M−H]⁺) was also tentatively identified in the methanol and water extracts. The methanol extract (1464.08 mg Trolox equivalent [TE]/g extract) showed the highest activity in the CUPRAC assay, whereas the water extract (1063.70 mg TE/g extract) showed the highest activity with the FRAP technique. The ethyl acetate extract was the most active acetylcholinesterase (4.43 mg galantamine equivalent/g extract) and α-glucosidase (mmol acarbose equivalent /g extract) inhibitor. The water extract was able to inhibit 5-HT-stimulated viability of HCT116 cells, and blunt 5-HT-induced reduction of cell-deriving KA. The scientific data generated in this study provide baseline data regarding the biological properties of B. abyssinica stem bark, highlighting its potential use for the development of new pharmaceutic and cosmetic agents.

Tazarotene-Induced Gene 1 (TIG1) Interacts with Serine Protease Inhibitor Kazal-Type 2 (SPINK2) to Inhibit Cellular Invasion of Testicular Carcinoma Cells

Tazarotene-induced gene 1 (TIG1) encodes a protein that is a retinoid-regulated tumor suppressor. TIG1 is expressed in most normal tissues, and downregulation of TIG1 expression in multiple cancers is caused by promoter hypermethylation. Kazal-type serine protease inhibitor-2 (SPINK2) is a serine protease inhibitor, and the SPINK protein family has been shown to inhibit the expression of urokinase-type plasminogen activator (uPA). In addition, increased levels of uPA and the uPA receptor were observed in testicular cancer tissues. This study demonstrated that TIG1 interacts with SPINK2 in NT2/D1 testicular carcinoma cells. TIG1 and SPINK2 were highly expressed in normal testis tissues, while low expression levels of TIG1 and SPINK2 were found in testicular cancer tissues. TIG1 inhibited cell invasion, migration, and epithelial-mesenchymal transition (EMT) of NT2/D1 cells. SPINK2 enhanced TIG1-regulated uPA activity and EMT suppression, while silencing SPINK2 alleviated TIG1-mediated EMT regulation, cell migration, and invasion. Therefore, the results suggest that the interaction between TIG1 and SPINK2 plays an important role in the inhibition of testicular cancer cell EMT, and suppression is mediated through downregulation of the uPA/uPAR signaling pathway.

Qualitative Fingerprint Analysis and Multidirectional Assessment of Different Crude Extracts and Essential Oil from Wild Artemisia santonicum L

Artemisia species are used as folk medicines in several countries. This work was aimed to shed more light on the effect of methanol, water, ethyl acetate extracts, and essential oil (EO) of A. santonicum on selected enzymes (cholinesterase, tyrosinase α-amylase, and α-glucosidase) as well of their antioxidant and pharmacological effects. The chemical profile of the essential oil was determined using gas chromatography coupled to mass spectrometry (GC-MS) analysis, while the extracts were chemically characterized by high performance liquid chromatography coupled to mass spectrometry (HPLC-MS). Forty-nine constituents were identified and camphor (36.6%), 1,8-cineole (10.2%), α-thujone (10.1%), borneol (4.5%), and β-thujone (3.6%) were the major components. Overall, 45, 74, and 67 components were identified from the ethyl acetate, methanol, and water extracts, respectively. The EO and extracts showed significant antioxidant properties, in a cell-free model; particularly, methanol and water extracts revealed promising sources of antioxidant compounds. Additionally, we evaluated protective effects of EO and extracts in isolated rat colon tissue challenged with lipopolysaccharide (LPS), as an ex vivo model of colon inflammation, and human colon cancer HCT116 cell line. Particularly, we observed that, among all tested samples, A. santonicum ethyl acetate displayed the best pharmacological profile, being able to blunt LPS-induced levels of all tested biomarkers of inflammation and oxidative stress, including colon nitrites, lactate dehydrogenase, prostaglandin E2, and serotonin. Additionally, this extract was also able to reduce HCT116 cell viability, thus suggesting potential antiproliferative effects against colon cancer cells. Based on our results, A. santonicum has great potential for developing novel functional agents including pharmaceuticals, cosmeceuticals, and nutraceuticals.

Prostaglandin E2 as a potent therapeutic target for treatment of colon cancer

Although colon cancer is one of the most important triggers of cancer related mortality, a few therapeutic options exist for this disease, including combination chemotherapy, anti-EGFR and anti-angiogenic agents. However, none of these therapeutics are fully effective for complete remission, and this issue needs further investigations, particularly in the patients with advanced disease. It has been shown that colon carcinogenesis process is associated with upregulation of prostaglandin (PG) levels. Moreover, conversion of pre-malignant cells to malignant was also related with increased generation of PGs in susceptible subjects. Among the prostanoids, PGE2 is the most important produced member which generated in high levels by colon tumor cells. Generation of PGE2 by action of cyclooxygenase (COX)-2 can promote growth and development, resistance to apoptosis, proliferation, invasion and metastasis, angiogenesis and drug resistance in colon cancer. Increased levels of PGE2 and COX-2 in colon cancer is reported by various investigators which was associated with disease progression. It is suggested that there is a positive feedback loop between COX-2 and PGE2, in which function of COX-2 induces generation of PGE2, and upregulation of PGE2 increases the expression of COX-2 in colon cancer. Although an existence of this feedback loop is well-documented, its precise mechanism, signaling pathways, and the particular E-type prostanoid (EP) receptor mediating this feedback are elusive. Therefore, it seems that targeting COX-2/PGE2/EP receptors may be supposed as a potent therapeutic strategy for treatment of colon cancer. In this review, we try to clarify the role of PGE2 in cancer progression and its targeting for treatment of colon cancer.

G-protein-coupled receptor kinase-5 promotes glioblastoma progression by targeting the nuclear factor kappa B pathway

G-protein-coupled receptor kinase-5 (GRK5) plays essential roles in multiple celluar events. However, its role in the development and progression of glioma is poorly understood. In this research, we found that GRK5 is significantly upregulated in human gliomas. For the first time, a close relationship was noted between GRK5 expression and blood vessel development in human glioma. Specifically co-expression of GRK5 and the tumor stem cell marker CD133 was observed in the cytoplasm of high grade glioma cells. The depletion of GRK5 suppressed the proliferation, migration and invasion in glioma cells, and promoted apoptosis. We next discovered that GRK5 knockdown inhibits the nuclear factor kappa B (NF-κB) pathway, thus resulting in downregulation of key downstream secretory products CCL2, IL-6 and IL-8 in glioma cell conditioned medium (CM). In addition, treatment of cells with the NF-κB stimulator PMA reversed this effect and increased the GRK5 level. Our results demonstrate an oncogenic role for GRK5 and reveal an activation of the GRK5-NF-κB pathway during the malignant progression of glioma.

Tazarotene-Induced Gene 1 Interacts with DNAJC8 and Regulates Glycolysis in Cervical Cancer Cells

The tazarotene-induced gene 1 (TIG1) protein is a retinoid-inducible growth regulator and is considered a tumor suppressor. Here, we show that DnaJ heat shock protein family member C8 (DNAJC8) is a TIG1 target that regulates glycolysis. Ectopic DNAJC8 expression induced the translocation of pyruvate kinase M2 (PKM2) into the nucleus, subsequently inducing glucose transporter 1 (GLUT1) expression to promote glucose uptake. Silencing either DNAJC8 or PKM2 alleviated the upregulation of GLUT1 expression and glucose uptake induced by ectopic DNAJC8 expression. TIG1 interacted with DNAJC8 in the cytosol, and this interaction completely blocked DNAJC8-mediated PKM2 translocation and inhibited glucose uptake. Furthermore, increased glycose uptake was observed in cells in which TIG1 was silenced. In conclusion, TIG1 acts as a pivotal repressor of DNAJC8 to enhance glucose uptake by partially regulating PKM2 translocation.

GRK5 functions as an oncogenic factor in non-small-cell lung cancer

Lung cancer is the leading cause of cancer-related deaths worldwide, and non-small-cell lung cancer (NSCLC) accounts for about 80% of all cases, which is the major subgroup of lung cancer. G protein-coupled receptor kinase 5 (GRK5) has been demonstrated to play pivotal roles in both development and progression of several pathological conditions including cancer. Here, we found that GRK5 expression was significantly increased in 539 NSCLC cancerous tissues than that in 99 normal non-cancerous tissues by immunohistochemistry analysis; we also showed intensive higher positive staining percentage in female and adenocarcinoma (ADC) NSCLC patients than that in male and squamous cell carcinoma (SCC) patients, respectively. In addition, GRK5 high expression NSCLC patients had a worse overall survival rate than the low expression patients. We provided evidence showing that both the mRNA and protein expression levels of GRK5 were increased in NSCLC cancerous cell lines (GLC-82, SPC-A-1, H520, H838, H358, A549, and H1299) comparing with that in normal human bronchial epithelium cell line (BEAS-2B), and identified many GRK5 mutations in NSCLC cancerous tissues. In addition, we found that depletion of GRK5 inhibited NSCLC cancerous cell proliferation, migration in vitro, and xenograft tumor formation in vivo. Furthermore, GRK5 knockdown promoted cell cycle arrest at G2/M phase and induced cellular apoptosis. In summary, our data reveal an oncogenic role of GRK5 in NSCLC progression, indicating that GRK5 could be used as a new therapeutic target in future.

Hypermethylation and loss of retinoic acid receptor responder 1 expression in human choriocarcinoma

Background

Human placental development resembles tumorigenesis, due to the invasive and fusogenic potential of trophoblasts. However, these features are tightly controlled in trophoblasts. Disturbance of this spatial and temporal regulation is thought to contribute to the rare formation of choriocarcinomas. Promoter hypermethylation and loss of the tumor suppressor Retinoic acid receptor responder 1 (RARRES1) were shown to contribute to cancer progression. Our study investigated the epigenetic and transcriptional regulation of RARRES1 in healthy human placenta in comparison to choriocarcinoma cell lines and cases.

Methods

Three choriocarcinoma cell lines (Jeg-3, JAR and BeWo) were treated with three different retinoic acid derivates (Am580, Tazarotene and all-trans retinoic acid) and 5-aza-2′-deoxycytidine. We analyzed RARRES1 promoter methylation by pyrosequencing and performed realtime-PCR quantification to determine RARRES1 expression in placental tissue and trophoblastic cell lines. Additionally, RARRES1 was stained in healthy placentas and in biopsies of choriocarcinoma cases (n = 10) as well as the first trimester trophoblast cell line Swan71 by immunofluorescence and immunohistochemistry.

Results

In the choriocarcinoma cell lines, RARRES1 expression could not be induced by sole retinoic acid treatment. Stimulation with 5-aza-2′-deoxycytidine significantly induced RARRES1 expression, which then could be further increased with Am580, Tazarotene and all-trans retinoic acid. In comparison to healthy placenta, choriocarcinoma cell lines showed a hypermethylation of the RARRES1 promoter, which correlated with a reduced RARRES1 expression. In concordance, RARRES1 protein expression was lost in choriocarcinoma tissue. Additionally, in the trophoblastic cell line Swan71, we found a significant induction of RARRES1 expression with increased cell density, during mitosis and in syncytial knots.

Conclusions

Our findings showed that RARRES1 expression is absent in choriocarcinoma due to promoter methylation. Based on our analysis, we hypothesize that RARRES1 might exert tumor suppressive functions in multiple cellular processes (e.g. cell cycle regulation, adhesion, invasion and apoptosis).

Electronic supplementary material

The online version of this article (10.1186/s13046-017-0634-x) contains supplementary material, which is available to authorized users.

Tazarotene-Induced Gene 1 Enhanced Cervical Cell Autophagy through Transmembrane Protein 192

Tazarotene-induced gene 1 (TIG1) is a retinoic acid-inducible protein that is considered a putative tumor suppressor. The expression of TIG1 is decreased in malignant prostate carcinoma or poorly differentiated colorectal adenocarcinoma, but TIG1 is present in benign or well-differentiated tumors. Ectopic TIG1 expression led to suppression of growth in cancer cells. However, the function of TIG1 in cell differentiation is still unknown. Using a yeast two-hybrid system, we found that transmembrane protein 192 (TMEM192) interacted with TIG1. We also found that both TIG1A and TIG1B isoforms interacted and co-localized with TMEM192 in HtTA cervical cancer cells. The expression of TIG1 induced the expression of autophagy-related proteins, including Beclin-1 and LC-3B. The silencing of TMEM192 reduced the TIG1-mediated upregulation of autophagic activity. Furthermore, silencing of either TIG1 or TMEM192 led to alleviation of the upregulation of autophagy induced by all-trans retinoic acid. Our results demonstrate that the expression of TIG1 leads to cell autophagy through TMEM192. Our study also suggests that TIG1 and TMEM192 play an important role in the all-trans retinoic acid-mediated upregulation of autophagic activity.

Topical Retinoids: Therapeutic Mechanisms in the Treatment of Photodamaged Skin

Retinoids are a group of substances comprising vitamin A and its natural and synthetic derivatives. Retinoids were first used in dermatology in 1943 by Straumfjord for acne vulgaris. Since that time, retinoids have been utilized in the management and treatment of various skin conditions, including photoaging. Photodamage of the skin occurs as a consequence of cumulative exposure to solar ultraviolet radiation (UVR) and is characterized by deep wrinkles, easy bruising, inelasticity, mottled pigmentation, roughness, and telangiectasias. The mechanism of UVR-induced photodamage is multifactorial. Retinoids have demonstrated efficacy in the treatment of photoaged skin. Indeed, understanding the pathophysiology of photoaging and the molecular mechanism of retinoids can not only provide insight into the effects retinoids can exert in treating photoaging but also provide the rationale for their use in the treatment of other dermatologic diseases.

Dual role of GRK5 in cancer development and progression

GRK5 is a multifunctional protein that is able to move within the cell in response to various stimuli to regulate key intracellular signaling from receptor activation, on plasmamembrane, to gene transcription, in the nucleus. Thus, GRK5 is involved in the development and progression of several pathological conditions including cancer. Several reports underline the involvement of GRK5 in the regulation of tumor growth even if they appear controversial. Indeed, depending on its subcellular localization and on the type of cancer, GRK5 is able to both inhibit cancer progression, through the desensitization of GPCR and non GPCR-receptors (TSH, PGE2R, PDGFR), and induce tumor growth, acting on non-receptor substrates (p53, AUKA and NPM1). All these findings suggest that targeting GRK5 could be an useful anti-cancer strategy, for specific tumor types. In this review, we will discuss the different effects of this kinase in the induction and progression of tumorigenesis, the molecular mechanisms by which GRK5 exerts its effects, and the potential therapeutic strategies to modulate them.

Tcf21 regulates the specification and maturation of proepicardial cells

The epicardium is a mesothelial cell layer essential for vertebrate heart development and pertinent for cardiac repair post-injury in the adult. The epicardium initially forms from a dynamic precursor structure, the proepicardial organ, from which cells migrate onto the heart surface. During the initial stage of epicardial development crucial epicardial-derived cell lineages are thought to be determined. Here, we define an essential requirement for transcription factor Tcf21 during early stages of epicardial development in Xenopus, and show that depletion of Tcf21 results in a disruption in proepicardial cell specification and failure to form a mature epithelial epicardium. Using a mass spectrometry-based approach we defined Tcf21 interactions and established its association with proteins that function as transcriptional co-repressors. Furthermore, using an in vivo systems-based approach, we identified a panel of previously unreported proepicardial precursor genes that are persistently expressed in the epicardial layer upon Tcf21 depletion, thereby confirming a primary role for Tcf21 in the correct determination of the proepicardial lineage. Collectively, these studies lead us to propose that Tcf21 functions as a transcriptional repressor to regulate proepicardial cell specification and the correct formation of a mature epithelial epicardium.

Analysis of tubulin alpha-1A/1B C-terminal tail post-translational poly-glutamylation reveals novel modification sites

Tubulin-α(1A/1B) C-terminal tail (CTT) has seven glutamic acid residues among the last 11 amino acids of its sequence that are potential sites for glutamylation. Cleavage of C-terminal tyrosine resulting in the detyrosinated form of tubulin-α(1A/1B) is another major modification. These modifications among others bring about highly heterogeneous tubulin samples in brain cells and microtubules, play a major role in directing intracellular trafficking, microtubule dynamics, and mitotic events, and can vary depending on the cell and disease state, such as cancer and neurodegenerative disorders. Identified previously using primary mass spectrometry (MS) ions and partial Edman sequencing, tubulin-α(1A/1B) glutamylation was found exclusively on the E(445) residue. We here describe the analysis of tubulin-α(1A/1B) glutamylation and detyrosination after 2-DE separation, trypsin and proteinase K in-gel digestion, and nanoUPLC-ESI-QqTOF-MS/MS of mouse brain and bovine microtubules. Tyrosinated, detyrosinated, and Δ2-tubulin-α(1A/1B) CTTs were identified on the basis of a comparison of fragmentation patterns and retention times between endogenous and synthetic peptides. Stringent acceptance criteria were adapted for the identification of novel glutamylation sites. In addition to the previously identified site at E(445), glutamylation on mouse and bovine tubulin-α(1A/1B) CTTs was identified on E(441) and E(443) with MASCOT Expect values below 0.01. O-Methylation of glutamates was also observed.