Inhibitory effects of Rap1GAP overexpression on proliferation and migration of endothelial cells via ERK and Akt pathways

Evaluation of Rap1GAP and EPAC1 Gene Expression in Endometriosis Disease

Background

Endometriosis is a female reproductive system disease in which the endometrial tissue is found in other women's organs. Various factors are effective in the development of endometriosis, and because of the interaction of genetics and environmental factors, this disease is a multi-factorial disease. MAPK/ERK and PI3K/Akt/mTOR pathways are activated by growth factors and steroid hormones and are known as two important pathways involved in the processes of growth, proliferation, and survival of endometriosis cells. Raps, monomeric GTPase of the Ras family, are able to activate these pathways independent of Ras. The goal of our study was to evaluate the expression level of Rap1GAP and EPAC1 genes as two important RapGAPs (GTPase-activating proteins) and RapGEFs (guanine nucleotide exchange factors), respectively, in endometriosis tissues and normal endometrium tissues.

Materials and Methods

In this study, 15 samples of women without signs of endometriosis were taken as control samples. Fifteen ectopic and 15 eutopic samples were taken from women with endometriosis using laparoscopic surgery. The expression of EPAC1 and Rap1GAP genes was investigated by the real-time polymerase chain reaction technique, and the results were analyzed by one-way ANOVA test.

Results

EPAC1 upregulated significantly in ectopic tissues compared to eutopic and control tissues. Rap1GAP expression was lower in ectopic tissues compared to control and eutopic tissues.

Conclusions

Based on these results, it may be concluded that changes in the expression of the Rap1GAP and Epca1 genes may play a role in the pathways involved in the pathogenesis, displacement, and migration of endometriosis cells.

Mex3a promotes oncogenesis through the RAP1/MAPK signaling pathway in colorectal cancer and is inhibited by hsa-miR-6887-3p

Background

Although Mex3 RNA‐binding family member A (Mex3a) has demonstrated an important role in multiple cancers, its role and regulatory mechanism in CRC is unclear. In this study, we aimed to investigate the role and clinical significance of Mex3a in CRC and to explore its underlying mechanism.

Methods

Western blotting and quantitative real‐time polymerase chain reaction (qRT‐PCR) were performed to detect the expression levels of genes. 5‐Ethynyl‐2'‐deoxyuridine (EDU) and transwell assays were utilized to examine CRC cell proliferation and metastatic ability. The R software was used to do hierarchical clustering analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Overexpression and rescue experiments which included U0126, a specific mitogen activated protein kinase kinase/extracellular regulated protein kinase (MEK/ERK) inhibitor, and PX‐478, a hypoxia‐inducible factor 1 subunit alpha (HIF‐1α) inhibitor, were used to study the molecular mechanisms of Mex3a in CRC cells. Co‐immunoprecipitation (Co‐IP) assay was performed to detect the interaction between two proteins. Bioinformatics analysis including available public database and Starbase software (starbase.sysu.edu.cn) were used to evaluate the expression and prognostic significance of genes. TargetScan (www.targetscan.org) and the miRDB (mirdb.org) website were used to predict the combination site between microRNA and target mRNA. BALB/c nude mice were used to study the function of Mex3a and hsa‐miR‐6887‐3p in vivo.

Results

Clinicopathological and immunohistochemical (IHC) studies of 101 CRC tissues and 79 normal tissues demonstrated that Mex3a was a significant prognostic factor for overall survival (OS) in CRC patients. Mex3a knockdown substantially inhibited the migration, invasion, and proliferation of CRC cells. Transcriptome analysis and mechanism verification showed that Mex3a regulated the RAP1 GTPase activating protein (RAP1GAP)/MEK/ERK/HIF‐1α pathway. Furthermore, RAP1GAP was identified to interact with Mex3a in Co‐IP experiments. Bioinformatics and dual‐luciferase reporter experiments revealed that hsa‐miR‐6887‐3p could bind to the 3'‐untranslated regions (3'‐UTR) of the Mex3a mRNA. hsa‐miR‐6887‐3p downregulated Mex3a expression and inhibited the tumorigenesis of CRC both in vitro and in vivo.

Conclusions

Our study demonstrated that the hsa‐miR‐6887‐3p/Mex3a/RAP1GAP signaling axis was a key regulator of CRC and Mex3a has the potential to be a new diagnostic marker and treatment target for CRC.

RNA sequencing analysis reveals increased expression of interferon signaling genes and dysregulation of bone metabolism affecting pathways in the whole blood of patients with osteogenesis imperfecta

BACKGROUND

Osteogenesis imperfecta (OI) is a rare genetic disorder in which the patients suffer from numerous fractures, skeletal deformities and bluish sclera. The disorder ranges from a mild form to severe and lethal cases. The main objective of this pilot study was to compare the blood transcriptional landscape of OI patients with COL1A1 pathogenic variants and their healthy relatives, in order to find out different gene expression and dysregulated molecular pathways in OI.

METHODS

We performed RNA sequencing analysis of whole blood in seven individuals affected with different OI severity and their five unaffected relatives from the three families. The data was analyzed using edgeR package of R Bioconductor. Functional profiling and pathway analysis of the identified differently expressed genes was performed with g:GOSt and MinePath web-based tools.

RESULTS

We identified 114 differently expressed genes. The expression of 79 genes was up-regulated, while 35 genes were down-regulated. The functional analysis identified a presence of dysregulated interferon signaling pathways (IFI27, IFITM3, RSAD12, GBP7). Additionally, the expressions of the genes related to extracellular matrix organization, Wnt signaling, vitamin D metabolism and MAPK-ERK 1/2 pathways were also altered.

CONCLUSIONS

The current pilot study successfully captured the differential expression of inflammation and bone metabolism pathways in OI patients. This work can contribute to future research of transcriptional bloodomics in OI. Transcriptional bloodomics has a strong potential to become a major contributor to the understanding of OI pathological mechanisms, the discovery of phenotype modifying factors, and the identification of new therapeutic targets. However, further studies in bigger cohorts of OI patients are needed to confirm the findings of the current work.

The Role of Ras-Associated Protein 1 (Rap1) in Cancer: Bad Actor or Good Player?

Metastasis is known as the most life-threatening event in cancer patients. In principle, the immune system can prevent tumor development. However, dysfunctional T cells may fail to eliminate the tumor cells effectively and provide additional survival advantages for tumor proliferation and metastasis. Constitutive activation of Ras-associated protein1 (Rap1) has not only led to T cell anergy, but also inhibited autophagy and supported cancer progression through various oncogenic events. Inhibition of Rap1 activity with its negative regulator, Rap1GAP, impairs tumor progression. However, active Rap1 reduces tumor invasion in some cancers, indicating that the pleiotropic effects of Rap1 signaling in cancers could be cancer-specific. All in all, targeting Rap1 signaling and its regulators could potentially control carcinogenesis, metastasis, chemoresistance and immune evasion. Rap1GAP could be a promising therapeutic target in combating cancer.

G Protein-Coupled Estrogen Receptor 1 Inhibits Angiotensin II-Induced Cardiomyocyte Hypertrophy via the Regulation of PI3K-Akt-mTOR Signalling and Autophagy

Estrogen has been demonstrated to protect the heart against cardiac remodelling and heart failure in women. G protein-coupled estrogen receptor 1 (GPER1) is a recently discovered estrogen receptor (ER) that is expressed in various tissues. However, the mechanisms by which estrogen protects the heart, especially the roles played by ERs, are not clear. In this study, we explored the effect of GPER1 activation on angiotensin II (Ang II)-induced cardiomyocyte hypertrophy and the involved signalling pathways and mechanisms. Our data demonstrated that GPER1 is expressed in cardiomyocytes, a GPER1 agonist, G1, attenuated Ang II-induced cardiomyocyte hypertrophy and downregulated the mRNA expression levels of atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP). Bioinformatics analysis revealed that five proteins, including RAP1gap, might be the key proteins involved in the attenuation of Ang II-induced cardiomyocyte hypertrophy by GPER1. G1 increased the protein level of p-Akt, p-70S6K1 and p-mTOR but decreased p-4EBP1 expression. All these effects were inhibited by either G15 (a GPER1 antagonist) or MK2206 (an inhibitor of Akt). Autophagy analysis showed that the LC3II/LC3I ratio was increased in Ang II-treated cells, and the increase was inhibited by G1 treatment. The effect of G1 on autophagy was blocked by treatment with G15, rapamycin, and MK2206. These results suggest that GPER1 activation attenuates Ang II-induced cardiomyocyte hypertrophy by upregulating the PI3K-Akt-mTOR signalling pathway and inhibiting autophagy.

Downregulation of Rap1Gap: A Switch from DCIS to Invasive Breast Carcinoma via ERK/MAPK Activation

Diagnosis of breast ductal carcinoma in situ (DCIS) presents a challenge since we cannot yet distinguish those cases that would remain indolent and not require aggressive treatment from cases that may progress to invasive ductal cancer (IDC). The purpose of this study is to determine the role of Rap1Gap, a GTPase activating protein, in the progression from DCIS to IDC. Immunohistochemistry (IHC) analysis of samples from breast cancer patients shows an increase in Rap1Gap expression in DCIS compared to normal breast tissue and IDCs. In order to study the mechanisms of malignant progression, we employed an in vitro three-dimensional (3D) model that more accurately recapitulates both structural and functional cues of breast tissue. Immunoblotting results show that Rap1Gap levels in MCF10.Ca1D cells (a model of invasive carcinoma) are reduced compared to those in MCF10.DCIS (a model of DCIS). Retroviral silencing of Rap1Gap in MCF10.DCIS cells activated extracellular regulated kinase (ERK) mitogen-activated protein kinase (MAPK), induced extensive cytoskeletal reorganization and acquisition of mesenchymal phenotype, and enhanced invasion. Enforced reexpression of Rap1Gap in MCF10.DCIS-Rap1GapshRNA cells reduced Rap1 activity and reversed the mesenchymal phenotype. Similarly, introduction of dominant negative Rap1A mutant (Rap1A-N17) in DCIS-Rap1Gap shRNA cells caused a reversion to nonmalignant phenotype. Conversely, expression of constitutively active Rap1A mutant (Rap1A-V12) in noninvasive MCF10.DCIS cells led to phenotypic changes that were reminiscent of Rap1Gap knockdown. Thus, reduction of Rap1Gap in DCIS is a potential switch for progression to an invasive phenotype. The Graphical Abstract summarizes these findings.

Rap1 promotes proliferation and migration of vascular smooth muscle cell via the ERK pathway

BACKGROUND

Rap1 is involved in a multitude of cellular signal transduction pathways, which has extensively been linked to cell proliferation and migration. It has been shown to be important in the regulation of physiological and pathological processes. The present study aims to elucidate its detailed mechanistic in proliferation and migration.

MATERIAL/METHODS

Vascular smooth muscle cells (VSMCs) were transfected with pcDNA3.1(empty vector), pcDNA3.1 containing Myc-Tagged-Rap1V12 (Rap1V12) or pcDNA3.1 containing Flag-Tagged-Rap1GAP (Rap1GAP).The cells were presence or absence with 8CPT-2'OMe-cAMP or SDF-1 before transfection. The proliferation and migration were examined by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) and transwell analysis, respectively. Afterwards, western blot was performed to detect the expression of ERK, phosphorylated-ERK, Rap1, Rap1GAP and Rap1GTP.

RESULTS

The results showed that proliferation, migration and the expression of Rap1, Rap1GAP, p-EKR were boosted in treatment of Rap1V12-transfection. However, Rap1GAP presented the opposite effects. Subsequently, VSMCs were pretreatment with stimulators Rap1 guanine exchange factor (Rap1GEF), 8CPT-2'OMe-cAMP and stromal cell-derived factor 1 (SDF-1), then transfected with different vectors and the expression of Rap1, Rap1GAP and p-EKR were obviously decreased.

CONCLUSIONS

Taken together, these findings indicated for the first time that Rap1 was essential for the VSMCs in proliferation and migration by ERK signaling pathway.

Ras and Rap1: A tale of two GTPases

Ras oncoproteins play pivotal roles in both the development and maintenance of many tumor types. Unfortunately, these proteins are difficult to directly target using traditional pharmacological strategies, in part due to their lack of obvious binding pockets or allosteric sites. This obstacle has driven a considerable amount of research into pursuing alternative ways to effectively inhibit Ras, examples of which include inducing mislocalization to prevent Ras maturation and inactivating downstream proteins in Ras-driven signaling pathways. Ras proteins are archetypes of a superfamily of small GTPases that play specific roles in the regulation of many cellular processes, including vesicle trafficking, nuclear transport, cytoskeletal rearrangement, and cell cycle progression. Several other superfamily members have also been linked to the control of normal and cancer cell growth and survival. For example, Rap1 has high sequence similarity to Ras, has overlapping binding partners, and has been demonstrated to both oppose and mimic Ras-driven cancer phenotypes. Rap1 plays an important role in cell adhesion and integrin function in a variety of cell types. Mechanistically, Ras and Rap1 cooperate to initiate and sustain ERK signaling, which is activated in many malignancies and is the target of successful therapeutics. Here we review the role activated Rap1 in ERK signaling and other downstream pathways to promote invasion and cell migration and metastasis in various cancer types.

The Different Effects of VEGFA121 and VEGFA165 on Regulating Angiogenesis Depend on Phosphorylation Sites of VEGFR2

The effects of VEGFA isoforms on the vascular permeability and structure are still unclear. In this study, we found that VEGFA121 and VEGFA165, 2 isoforms of VEGFA, exerted the opposing effects of antiangiogenesis and proangiogenesis on regulating vascular endothelia cells proliferation and tube formation. The 2 isoforms affected the protein expression of Ras-related protein 1-GTPase-activating protein 1 (Rap1GAP) and thrombospondin 1, 2 important signal molecules of Rap1GAP/thrombospondin 1 signal pathway in primary human umbilical vein endothelial cells by regulating 2 different phosphorylating sites of VEGFR2, Tyr(1175) and Tyr(1214). We also found that VEGFA121 and VEGFA165 regulating angiogenesis was related to their regulating VEGFR2 and Rap1GAP/thrombospondin 1 signal pathway with the technology of RNA intervening the gene expression of VEGFR2 and Rap1GAP. Meanwhile, 2 inhibitors of VEGFR2, cabozantinib malate and ZM 323881 HCl (ZM), were used to investigate the relationship among VEGFA(121 and 165), VEGFR2, and angiogenesis. It was demonstrated that cabozantinib malate blocked VEGFA121 and VEGFA165 binding to VEGFR2 and inhibited angiogenesis by specifically binding to VEGFR2 rather than changing VEGFR2 phosphorylation or regulating the expression of VEGFR2. However, ZM antagonized the effect of VEGFA on angiogenesis by specifically reversing the phosphorylation induced by VEGFA121 and VEGFA165. The experiments in vivo also demonstrated that obvious abnormality of VEGFA121 and VEGFA165 presented in the serum of ulcerative colitis (UC) rats compared with that of the normal rats. ZM could promote the repairation of the injuries of the vessels and tissues of colonic mucosa of UC rats and caused mild inflammation in colonic mucosa of normal rats. On the contrary, cabozantinib malate caused injury of vessels and inflammation in the colonic mucosa of normal rats and aggravated the injuries of the vessels and inflammation in the colonic mucosa of UC rats. Hence, our data indicated that the activation of different phosphorylation sites of VEGFR2 leaded to VEGFA121 and VEGFA165 exerting opposing effects on angiogenesis, and it might be an underlying pathogenesis of UC and a potential target for UC treatment.

Cooperation of Epac1/Rap1/Akt and PKA in prostaglandin E(2) -induced proliferation of human umbilical cord blood derived mesenchymal stem cells: involvement of c-Myc and VEGF expression

Prostaglandin E(2) (PGE(2)) is well known to regulate cell functions through cAMP; however, the role of exchange protein directly activated by cAMP (Epac1) and protein kinase A (PKA) in modulating such functions is unknown in human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs). Therefore, we investigated the relationship between Epac1 and PKA during PGE(2)-induced hUCB-MSC proliferation and its related signaling pathways. PGE(2) increased cell proliferation, and E-type prostaglandin (EP) 2 receptor mRNA expression level and activated cAMP generation, which were blocked by EP2 receptor selective antagonist AH 6809. PGE(2) increased Epac1 expression, Ras-related protein 1 (Rap1) activation level, and Akt phosphorylation, which were inhibited by AH 6809, adenylyl cyclase inhibitor SQ 22536, and Epac1/Rap1-specific siRNA. Also, PGE(2) increased PKA activity, which was inhibited by AH 6809, SQ 22536, and PKA inhibitor PKI. HUCB-MSCs were incubated with the Epac agonist 8-pCPT-cAMP or the PKA agonist 6-phe-cAMP to examine whether Epac1/Rap1/Akt activation was independent of PKA activation. 8-pCPT-cAMP increased Akt phosphorylation but not PKA activity. 6-Phe-cAMP increased PKA activity, but not Akt phosphorylation. Additionally, an Akt inhibitor or PKA inhibitor (PKI) did not block the PGE(2) -induced increase in PKA activity or Akt phosphorylation, respectively. Moreover, PGE(2) increased glycogen synthase kinase (GSK)-3β phosphorylation and nuclear translocation of active-β-catenin, which were inhibited by Akt inhibitor or/and PKI. PGE(2) increased c-Myc and vascular endothelial growth factor (VEGF) expression levels, which were blocked by β-catenin siRNA. In conclusion, PGE(2) stimulated hUCB-MSC proliferation through β-catenin-mediated c-Myc and VEGF expression via Epac/Rap1/Akt and PKA cooperation.