Questions have been raised about the genomic complexity of the human genome, since it was reported that it only consisted of 32,000 genes. Alternative splicing is considered the explanation of the enormous difference between the number of genes and the number of proteins. Aligning expressed sequence tags (ESTs) to the genomic sequence has become a popular approach for gene prediction, revealing alternative splice variants. The aim in this thesis is to identify and analyse splice variants of the adhesion family of G protein-coupled receptors using EST data. 75% of the genes in the data set of 33 sequences were found to have a total of 51 splice variants. About half of the variants were considered functional.

<p>Questions have been raised about the genomic complexity of the human genome, since it was reported that it only consisted of 32,000 genes. Alternative splicing is considered the explanation of the enormous difference between the number of genes and the number of proteins. Aligning expressed sequence tags (ESTs) to the genomic sequence has become a popular approach for gene prediction, revealing alternative splice variants. The aim in this thesis is to identify and analyse splice variants of the adhesion family of G protein-coupled receptors using EST data. 75% of the genes in the data set of 33 sequences were found to have a total of 51 splice variants. About half of the variants were considered functional.</p>

Growth factor receptors have significant effects on various normal function of body such as cell proliferation, differentiation and apoptosis. They are also involved in neuronal function and dysfunction, cardiovascular diseases, and malignancies. Recently, multiple G protein-coupled receptors (GPCRs) have been shown to transactivate receptor tyrosine kinases (RTKs). Since both classes of receptors have complicated downstream cascades individually, understanding the signaling differences between GPCR-induced growth factor receptor transactivation and direct ligand activation is an important challenge. To clarifying this phenomenon we investigated the phosphorylation profile and downstream effectors of ligand-activated vs. transactivated PDGF?? receptors. Dopamine receptors (one of the receptors of the GPCRs family) were used to compare the PDGF?? receptor phosphorylation and activity during direct activation and transactivation. Dose-response and time-course data between these two stimuli were evaluated. Furthermore, the phosphorylation site profiles and the intracellular signaling pathways of PDGF?? receptor after direct activation and transactivation were examined. In addition, possible synergic effects between transactivation and direct activation were explored. The results of this project showed that the phosphorylation profile and downstream effectors of ligand activated receptors versus transactivated receptors are different. Our data indicated that transactivation-induced pathways are more involved in survival and proliferation effects compared to ligand activation. This research answered basic questions about transactivation phenomena and proposes that these transactivation pathways could be exploited as a therapeutic approach for neurodegenerative diseases.

The mechanisms that regulate the differentiation of stem cells (SCs) into cardiomyocytes are still unclear and the role of endogenous molecules on this process remains unexplored. One such molecule is the bioactive phospholipid lysophosphatidic acid (LPA) which accumulates in the myocardium following acute infarction and exerts multiple biological functions, including the regulation of cell growth and differentiation as well as cell survival (Tigyi et al., 2003; Sengupta, et al., 2004). Experiments were therefore carried out in this thesis to reveal whether LPA can induce the differentiation of stem cells into cardiomyocytes and to identify the signalling mechanisms that mediate this effect. All experiments were carried out in the mouse P19 carcinoma stem cell line. Treatments with LPA in the absence and presence of various pharmacological compounds were conducted in embryoid bodies (EBs) formed from the P19 cells in sterile Petri dishes over 4 days. The EBs were subsequently transferred into 6-well cell culture plates and cultured for specific time points. Lysates were generated and subjected to western blotting for expression of cardiac- specific myosin light chain -1v (MLC-1v). To look at the expression of LPA receptors (LPAR1-LPAR5) experiments were carried out by RT-PCR using specific primers for each LPA receptor and the role of the latter in mediated responses to LPA were examined in the presence of the LPAR 1/3 antagonist, Ki16425, or the LPAR 4 receptor blocker suramin. In addition, experiments were carried out investigating the role of Gαi and specific signalling pathways that may be involved in the differentiation of P19 cells. These were carried out using potent inhibitors/antagonists of Gαi inhibitor (Pertussis toxin), PI3K inhibitor (LY294002), Akt inhibitor (Akt inhibitor XIII), PKC inhibitor (Bisindolylmaleimide I BIM-I), ROCK inhibitor (Y-27632), p38-MAPK inhibitor (SB203580) and ERK1/2 inhibitor (PD98059). Further experiments were carried out to establish whether the presence of LPA results in the phosphorylation of the targeted kinases. These studies were however limited to Akt, p38 MAPK and ERK1/2. Incubation of cells with LPA resulted in the differentiation of P19 cells into cardiomyocytes as reflected by the induction of MLC-1v. The latter increased significantly above basal in a time-dependent manner, reaching a maximum 10 days after plating EBs in 6-well plates. The induction of MLC-1v was more pronounced in cells incubated with 5 μM LPA at 6 days but showed little concentration differences at day 12. RT-PCR analysis confirmed the expression of LPA receptors 1 to 4 but not 5. Pre-incubating cells with suramin and Ki16425 concentration-dependently inhibited MLC-1v expression with 0.05 mg/ml and 10 μM respectively, virtually abolishing the expression of MLC-1v. Additionally, inhibitors of LPAR1/3 and LPAR4 receptors and all the signalling inhibitors except SB203580 abolished the phosphorylation of ERK1/2. Similarly, p38 MAPK activation was completely abolished by LPAR1/3 and LPAR4 receptor antagonists, Interestingly, only LY294002 (5 μM) and Y27632 (10 μM) abolished the LPA induced activation of p38 MAPK while SB203580, BIM-I, Akt inhibitor XIII and PD95080 caused no significant changes to the phosphorylation of p38 MAPK. In conclusion, the studies carried out in this thesis have shown that LPA can induce P19 stem cells to differentiate into cardiomyocytes and they are linked to the well characterised LPA receptors (LPAR1/3 and 4). These receptors are coupled to downstream signalling pathways of which those involving the ROCK, PI3K, PKC and/or Akt may be critical, and may converge on ERK1/2. Inhibition of any of these pathways has the potential to suppress differentiation. In contrast, signalling leading to p38 activation may potentially suppress differentiation but this needs further clarification.

L'immunothérapie, en particulier l'utilisation d'inhibiteurs de PD-1 et de PD-L1, a révolutionné le traitement du cancer. Cependant, son efficacité varie, certains patients présentant une réponse limitée ou une rechute, souvent liée à une forte expression de PD-L1 dans le microenvironnement tumoral. Des recherches récentes suggèrent que les effecteurs de la voie Hippo, YAP et TAZ, pourraient jouer un rôle crucial dans la régulation de l'expression de PD-L1 dans les cellules cancéreuses, y compris celles du sein et du poumon. La voie Hippo, qui contrôle la survie cellulaire, la prolifération et la taille des organes, agit par l'inhibition médiée par la kinase Lats1/2 de YAP/TAZ. Lorsqu'ils ne sont pas phosphorylés, YAP/TAZ se déplacent vers le noyau, affectant l'expression de gènes tels que PD-L1 et PD-1. De plus, les récepteurs couplés aux protéines G (RCPG), y compris le récepteur de type 1 à l'angiotensine II (AT1), ont été identifiés comme des modulateurs potentiels de la réponse immunitaire dans le cancer. Cette étude vise à développer et valider de nouveaux biosenseurs basés sur la BRET pour observer l'activité de la voie Hippo en suivant le mouvement de YAP et de TAZ du cytoplasme au noyau et pour évaluer la capacité de ces capteurs à surveiller différents signaux stimulants, y compris la stimulation AT1R, offrant ainsi des aperçus de nouvelles stratégies thérapeutiques en immuno-oncologie. L'immunothérapie est apparue comme une approche révolutionnaire pour pallier les limites des traitements anticancéreux traditionnels, introduisant des médicaments ciblant les points de contrôle immunitaires, tels que les inhibiteurs de PD-1 (protéine de mort cellulaire programmée 1) et de PD-L1 (ligand de mort cellulaire programmée 1). Cependant, certains patients présentent une réponse inadéquate ou une rechute après traitement, notamment ceux avec une expression accrue de PD-L1 dans le microenvironnement tumoral. En conséquence, la modulation de PD-1 et de PD-L1 émerge comme une branche potentielle des thérapies immuno-basées. Des investigations récentes suggèrent que les effecteurs de la voie Hippo, YAP et TAZ, pourraient influencer la réponse immunitaire en régulant transcriptionnellement PD-L1 dans diverses cellules cancéreuses, y compris celles du sein et du poumon. Mécanistiquement, la kinase Lats1/2 inhibe YAP/TAZ par phosphorylation directe, les séquestrant dans le cytoplasme, tandis que YAP/TAZ non phosphorylés se transloquent dans le noyau, médiatisant la sortie transcriptionnelle de gènes tels que PD-L1 et PD-1. La signalisation des RCPG a été proposée comme un modulateur 4 potentiel de la réponse immunitaire au cancer, avec le récepteur de type 1 à l'angiotensine II (AT1) suggéré comme un médicament combiné potentiel pour les traitements en immunooncologie. Par conséquent, ce travail vise à développer et valider de nouveaux biosenseurs basés sur la BRET pour évaluer la voie Hippo en surveillant la translocation de YAP et de TAZ du cytoplasme au noyau et pour évaluer la capacité de ces capteurs à surveiller différents signaux stimulants, y compris la stimulation AT1R. Cette étude visait à développer et à valider des biosenseurs pour surveiller l'activité de la voie Hippo en évaluant la translocation de YAP et de TAZ à l'aide du transfert d'énergie de résonance bioluminescente améliorée (ebBRET). Des défis techniques ont entravé la validation complète sous différents stimuli, mais la manipulation de la densité cellulaire a validé la fonctionnalité du capteur. L'identification du récepteur AT1 comme un modulateur de la relocalisation de YAP médiée par les RCPG souligne la nécessité d'explorer l'interaction entre la signalisation des RCPG et la voie Hippo. La sélection minutieuse des activateurs et la validation complète sont cruciales pour élucider le réseau régulateur de YAP/TAZ dans le développement du cancer. / Immunotherapy, particularly the use of PD-1 and PD-L1 inhibitors, has revolutionized cancer treatment. However, its effectiveness varies, with some patients showing limited response or relapse, often linked to high PD-L1 expression in the tumor microenvironment. Recent research suggests that the Hippo pathway effectors, YAP and TAZ, may play a crucial role in regulating PDL1 expression in cancer cells, including breast and lung cancers. The Hippo pathway, which controls cell survival, proliferation, and organ size, operates through the Lats1/2 kinase-mediated inhibition of YAP/TAZ. When not phosphorylated, YAP/TAZ move to the nucleus, affecting the expression of genes like PD-L1 and PD-1. Furthermore, G protein-coupled receptors (GPCRs), including the Angiotensin II type 1 (AT1) receptor, have been identified as potential modulators of the immune response in cancer. This study aims to develop and validate novel BRET-based biosensors to observe the Hippo pathway's activity by tracking the movement of YAP and TAZ from the cytoplasm to the nucleus and to assess various stimulatory signals, including AT1R stimulation, offering insights into new therapeutic strategies in immuno-oncology Immunotherapy has emerged as a revolutionary approach to address the limitations of traditional cancer treatments, introducing drugs that target immune checkpoints, such as PD-1 (Programmed Cell Death Protein 1) and PD-L1 (Programmed Cell Death Ligand 1) inhibitors. Yet, some patients exhibit inadequate response or experience relapse post-treatment, especially those with heightened PD-L1 expression in the tumor microenvironment. Consequently, modulation of PD-1 and PD-L1 has emerged as a potential branch of immuno-based therapies. Recent investigations propose that the Hippo pathway effectors, YAP and TAZ, may influence the immune response by transcriptionally regulating PD-L1 in various cancer cells, including breast and lung cancer. Mechanistically, Lats1/2 kinase inhibits YAP/TAZ through direct phosphorylation, leading to their sequestration in the cytoplasm, while unphosphorylated YAP/TAZ translocate to the nucleus, mediating the transcriptional output of genes such as PD-L1 and PD-1. G proteincoupled receptors (GPCRs) signaling has been proposed as a potential modulator of the immune response to cancer, with the Angiotensin II type 1 (AT1) receptor suggested as a potential combination drug for immune-oncology treatments. Therefore, this work aims to develop and validate new BRET-based biosensors to evaluate the Hippo pathway by monitoring the 6 translocation of YAP and Taz from the cytoplasm to the nucleus and to evaluate the ability of these sensors to monitor different stimulatory signals, including AT1R stimulation. This study aimed to develop and validate biosensors for monitoring Hippo pathway activity by assessing YAP and TAZ translocation using enhanced bioluminescence resonance energy transfer (ebBRET). Technical challenges hindered comprehensive validation under different stimuli, yet cell density manipulation validated sensor functionality. Identification of AT1 receptor as a modulator of GPCR-mediated YAP relocalization underscores the need to explore GPCR-Hippo pathway interplay. Meticulous activator selection and comprehensive validation are crucial for unraveling YAP/TAZ's regulatory network in cancer development.

It is widely known that early estimates about the binding properties of drug candidates are important in the drug discovery process. Surface plasmon resonance (SPR) biosensors have become a standard tool for characterizing interactions between a great variety of biomolecules and it offers a unique opportunity to study binding activity. The aim of this project was to develop a SPR based assay for pre-screening of low molecular weight (LMW) drug compounds, to enable filtering away disturbing compounds when interacting with drugs. The interaction between 47 LMW compounds and biological ligands were investigated using the instrument BiacoreTM, which is based on SPR-technology.