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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Sequence Specificity of BUZ, PDZ, SH2, and Tandem BRCT Domains

Hard, Ryan Lawrence January 2013 (has links)
No description available.
2

Biophysical analysis and NMR structural characterization of the binding between peptidomimetic drug CN2097 and scaffolding protein PSD-95

Hu, Tony Ken 12 June 2019 (has links)
BACKGROUND: At the postsynaptic membrane of neurons there is a dense network of proteins called the postsynaptic density (PSD). One such protein is the postsynaptic density protein 95 (PSD-95), which functions as a molecular scaffold for forming protein complexes at the PSD. PSD-95 is composed of three PDZ domains, which studies have shown to be sequentially and structurally similar. Studies have shown that PSD-95 plays a role in regulating signaling of glutamatergic neurons, as well as the induction of longterm potentiation through an association with TrkB receptors. PSD-95 may be a promising target for treatment of a number of neurological disorders such as depression, epilepsy, and cognitive dysfunction. The cyclic peptidomimetic drug CN2097 was designed based on the PDZ-binding motif of the CRIPT protein that binds to PDZ3. While CN2097 has been shown to affect the binding of PSD-95 to different synaptic proteins, no NMR studies have been performed to characterize the binding of CN2097 to PDZ3. Furthermore, few studies have characterized the inter-domain interactions between PDZ domains or whether the binding of calmodulin (CaM) to the N-terminal region of PSD-95 has any effect on the binding between the PDZ domains and CN2097. OBJECTIVE: To use isothermal titration calorimetry and nuclear magnetic resonance spectroscopy to analyze and characterize how CN2097 binds to PDZ domains and whether inter-domain interactions exist between PDZ domains. METHODS: The gene sequences for the PDZ domains were inserted into the pET28a(+) vector by subcloning. E. coli bacteria were then transformed with the different PDZ plasmids. The bacterial cells were grown and induced to express the proteins of interest, followed by lysis and purification using affinity chromatography and fast protein liquid chromatography (FPLC). Isothermal titration calorimetry (ITC) was used to measure the dissociation constant and thermodynamic binding parameters between the peptidomimetic drug CN2097 and each isolated PDZ domain. Nuclear magnetic resonance (NMR) spectroscopy was used to study how CN2097 binds to PDZ1 and PDZ3, and how the PDZ domains interact with each other. RESULTS: The ITC data showed the dissociation constant between CN2097 and PDZ3 to be 5.12 ± (1.65) μM, and that of PDZ2+3 to be 42.63 ± (6.11)μM. ITC data on other domains was inconclusive. The NMR data showed no interaction between N-terminal region and PDZ1, and between PDZ2 and PDZ3 but significant interaction was seen between PDZ1 and PDZ2, as well as between PDZ3 and the inter-domain linker connecting it to PDZ2. NMR data showed that CN2097 binding perturbs PDZ3 more strongly than PDZ1 and that CN2097 does not bind to PDZ1 in the presence of CaM. Significant NMR chemical shift perturbations are seen on the second α-helix, second β- sheet, and β2-β3 loop. CONCLUSIONS: There are no significant contacts between the N-terminal α-helix and PDZ1. There is inter-domain conformational exchange and interaction between PDZ1 and PDZ2. PDZ3 interacts with the second inter-domain linker. CN2097 binds tighter to PDZ3 than to PDZ1, and does not bind to PDZ1 in the presence of CaM. The β2-β3 loop is a prime target for future development of CN2097.
3

Vers une meilleure connaissance de la spécificité des interactions protéiques dans la signalisation cellulaire - les domaines PDZ au centre des approches informatiques et expérimentales / Towards a better understanding of protein interaction specificities in cell signalling - PDZ domains in the spotlight of computational and experimental approaches

Luck, Katja 19 October 2012 (has links)
Les domaines PDZ reconnaissent des motifs C-terminaux (PBMs), à l'origine de nombreuses interactions qui sont souvent impliquées dans la régulation de la polarité cellulaire. Dans cette thèse, nous avons étudié divers aspects de la spécificité des interactions PDZ-PBM. Nous avons mis en évidence les faibles performances de deux prédicteurs d'interaction entre PDZs et PBMs, considérés sous leurs formes les plus courtes. Ensuite, nous avons développé des protocoles basés sur les méthodes BIAcore et HoldUp pour valider expérimentalement et à grande échelle des prédicteurs d'interaction PDZ-PBM et pour étudier l'influence du contexte de séquence (comme les séquences flanquantes ou les domaines voisins) des PDZs et des PBMs sur l’affinité et la spécificité de leurs interactions. Nous avons identifié des interactions potentielles impliquant les protéines humaines à PDZ MAGI1 et SCRIB soulignant leur implication dans les réseaux de signalisation des protéines G. Une revue de la littérature, combinée avec nos propres résultats, a révélé des mécanismes par lesquels le contexte de séquence influence les affinités et spécificités des interactions impliquant les PDZs. Nous avons discuté ces mécanismes dans une revue publiée. Les connaissances obtenues à partir de cette thèse pourront influencer positivement de futures études sur les interactions PDZ-PBM, en particulier, et sur les interactions domaine-motif linéaire en général. / PDZ domains recognize C-terminal PDZ-binding motifs (PBMs) thereby mediating protein interactions that are often involved in cell polarity regulation. In this thesis, we studied under various aspects the specificity of PDZ-PBM interactions. We identified weak performances of two published predictors for interactions between core PDZ domains and short PBMs. Next, we developed protocols based on BIAcore and HoldUp to experimentally validate on a large scale predicted PDZ-PBM interactions and to study the influence of sequence context (e.g. flanking regions or neighbouring domains) of PDZs and PBMs on their interaction affinity and specificity. We identified new potential interactions involving the human PDZ proteins MAGI1 and SCRIB underpinning their implication in G protein signalling pathways. A literature survey combined with our own findings reveal structural mechanisms, by which sequence context influences PDZ interaction affinities and specificities. We have discussed those in a published review. Insights gained from this thesis may positively impact future studies on PDZ-PBM interactions in particular and on domain-linear motif interactions in general.
4

La MAP kinase p38γ influence la structure des cardiomyocytes

Plamondon, Philippe January 2014 (has links)
Le cœur est un organe central au fonctionnement du système cardiovasculaire. Il est physiologiquement compartimenté et est constitué de cellules spécialisées qui régulent les impulsions électriques ainsi que la contraction du myocarde. Le cœur adapte le flux sanguin en fonction des besoins du corps. En condition pathologique, le cœur recourt toutefois à des mécanismes compensatoires. Au niveau physiologique, la compensation s’observe par l’hypertrophie des cardiomyocytes qui, bien que bénéfique à court terme, exacerbe à long terme la fonction cardiaque. L’activation des « mitogen activated protein kinases » (MAPK) contribue autant au maintien de la fonction physiologique qu’à la détérioration pathologique du myocarde et serait également une cause de l’hypertrophie observée. Parmi les 5 groupes de MAPK connues, la MAPK p38 est formée de 4 isoformes dont les sérine/thréonine kinases p38α et p38γ sont exprimées de façon prédominante dans le cœur. Les p38 partagent les mêmes activateurs, mais leurs effecteurs diffèrent. Bien que le rôle de p38α semble impliqué dans l’aggravement des troubles cardiaques, celui de p38γ ne semble pas redondant à p38α et demeure incompris. Cette isoforme possède un motif de liaison aux domaines PDZ, unique chez les MAP kinases. Également, chez les cellules cardiaques, elle transloque au noyau en condition de stress. Le but de l’étude ici est de comprendre le rôle de p38γ et de ses motifs uniques sur la structure et la taille des cardiomyocytes. Afin de répondre au but de l’étude, plusieurs mutants adénoviraux de p38 ont été conçus. Un des mutants ne possède pas le motif de liaison aux domaines PDZ, deux autres contrôlent la localisation cellulaire soit au noyau, soit au cytoplasme, et un autre mutant est muté au site de phosphorylation. Des cardiomyocytes en culture ont été infectés par les différents mutants en présence de leur activateur en amont ou de la β-galactosidase. Les réseaux d’α-actinine, ainsi que la taille des cardiomyocytes, ont été observés par microscopie. Les observations effectuées montrent que p38γ entraîne une désorganisation des réseaux d’α-actinine lorsqu’il est phosphorylé. Également, il facilite l’hypertrophie des cardiomyocytes en présence de son activateur s’il est forcé hors du noyau ou en l’absence de son motif de liaison aux domaines PDZ. En conclusion, les résultats obtenus suggèrent que p38γ exerce bel et bien un rôle dans le maintien structural des cardiomyocytes par l’intermédiaire de l’α-actinine.
5

Characterization of the Physiological Role of PDZ-RhoGEF in Drosophila and Mice

Jang, Ying-Ju 15 September 2011 (has links)
Biological outputs of insulin/IGF signaling are regulated through essential mediators, such as IRSs, PI3-kinase, and PKB/Akt. These mediators serve critical roles in signal propagation, feedback, and as junctions for crosstalk with other pathways. Abnormal insulin/IGF signaling results in disease, such as obesity, diabetes, and cancer. Given the vital role of this signaling pathway to human health, unraveling its regulatory mechanisms is crucial. Components of this pathway are highly conserved throughout evolution. PTEN, one of the well-defined regulators of this pathway, functions as a lipid phosphatase that negatively regulates insulin/IGF-1 signaling at the PIP3 level, a phosphoinositol that is upregulated by activated PI3-kinase in both Drosophila and mammals. To discover genetic modulators of PTEN in Drosophila, we performed a loss-of-function genetic screen to identify molecules that modify the phenotype elicited by PTEN overexpression in the Drosophila eye. From this screen, we identified a member of the Dbl-family, the guanine nucleotide exchange factor DRhoGEF2, which suppresses the PTEN-overexpression eye phenotype via its effects on dPKB/dAkt activation. By conducting a genetic rescue, we established that PDZ-RhoGEF, a member of the regulator of G-protein signal (RGS)-like domain containing Rho GEFs (RGS-RhoGEFs) subfamily of Dbl-family GEFs, is the mammalian counterpart of DRhoGEF2. PDZ-RhoGEF is essential for cell proliferation and survival through ROCK-dependent activation of IRS/PI3-kinase signaling cascade, which has a major impact on adipose tissue homeostasis. Through an integrative approach, we have demonstrated that DRhoGEF2/PDZ-RhoGEF-dependent signaling has tissue-specific effects on insulin/IGF-signaling throughput in both Drosophila and mammals. Particularly, we have demonstrated the role played by PDZ-RhoGEF in diet related pathology, provides an alternative therapeutic opportunity in disease intervention.
6

Structural and thermodynamic origins of distinct ligand specificity of two homologous PDZ domains

Shepherd, Tyson Robert 01 July 2011 (has links)
Guanine nucleotide exchange factor proteins of the Tiam family are activators of the Rho GTPase Rac1 and critical for cell morphology, adhesion, migration, and polarity. These proteins are modular and contain a variety of interaction domains, including a previously uncharacterized post-synaptic density-95/discs large/zonula occludens-1 (PDZ) domain. Here we report on the structure, specificity, and function of the Tiam1 and Tiam2 PDZ domains. A consensus PDZ-binding motif for Tiam1 was used to predict that two cell adhesion proteins, Syndecan 1 (Sdc1) and Caspr4, are potential Tiam1 PDZ domain binding proteins. Binding interactions were confirmed using fluorescence- and NMR- based binding experiments. The Tiam1 PDZ domain in complex with the C-terminal tails of Sdc1 and phosphorylated Sdc1 were solved using X-ray crystallography. Results showed four residues in two binding pockets in the PDZ domain are important for specificity. Cell biological analysis confirmed the Tiam1/Sdc1 interaction and showed that the PDZ domain has a function in cell-matrix adhesion and cell migration. The four residues deemed important determinants of Tiam1 PDZ domain specificity are not conserved in Tiam2. A combinatorial peptide screen, in combination with biophysical studies, identified a consensus binding sequence for both PDZ domains. Analysis of these consensus sequences and binding assays with peptides derived from native proteins indicated that these two PDZ domains have overlapping but distinct specificities - the Tiam2 PDZ domain was found to bind Caspr4 and neurexin1 but not Sdc1. Additionally, the Tiam2 PDZ domain exhibits significant flexibility in two different regions, a feature not seen in Tiam1. Double-mutant cycle analysis of the four important residues revealed ligand- dependent energetic couplings. Mutating all four residues switched the ligand specificity to that of Tiam2. Analysis of Tiam-family PDZ domain sequences indicated that the PDZ domains segregate into four distinct families based on the residues studied here. A set of "evolved peptides" was used to show the PDZ domain interactions are cooperative throughout the binding pocket in a ligand-specific manner. Collectively, our data suggest that Tiam family proteins have highly evolved PDZ domain/ligand interfaces with distinct specificities and that they have disparate PDZ domain-dependent biological functions.
7

La MAP kinase p38γ influence la structure des cardiomyocytes

Plamondon, Philippe January 2014 (has links)
Le cœur est un organe central au fonctionnement du système cardiovasculaire. Il est physiologiquement compartimenté et est constitué de cellules spécialisées qui régulent les impulsions électriques ainsi que la contraction du myocarde. Le cœur adapte le flux sanguin en fonction des besoins du corps. En condition pathologique, le cœur recourt toutefois à des mécanismes compensatoires. Au niveau physiologique, la compensation s’observe par l’hypertrophie des cardiomyocytes qui, bien que bénéfique à court terme, exacerbe à long terme la fonction cardiaque. L’activation des « mitogen activated protein kinases » (MAPK) contribue autant au maintien de la fonction physiologique qu’à la détérioration pathologique du myocarde et serait également une cause de l’hypertrophie observée. Parmi les 5 groupes de MAPK connues, la MAPK p38 est formée de 4 isoformes dont les sérine/thréonine kinases p38α et p38γ sont exprimées de façon prédominante dans le cœur. Les p38 partagent les mêmes activateurs, mais leurs effecteurs diffèrent. Bien que le rôle de p38α semble impliqué dans l’aggravement des troubles cardiaques, celui de p38γ ne semble pas redondant à p38α et demeure incompris. Cette isoforme possède un motif de liaison aux domaines PDZ, unique chez les MAP kinases. Également, chez les cellules cardiaques, elle transloque au noyau en condition de stress. Le but de l’étude ici est de comprendre le rôle de p38γ et de ses motifs uniques sur la structure et la taille des cardiomyocytes. Afin de répondre au but de l’étude, plusieurs mutants adénoviraux de p38 ont été conçus. Un des mutants ne possède pas le motif de liaison aux domaines PDZ, deux autres contrôlent la localisation cellulaire soit au noyau, soit au cytoplasme, et un autre mutant est muté au site de phosphorylation. Des cardiomyocytes en culture ont été infectés par les différents mutants en présence de leur activateur en amont ou de la β-galactosidase. Les réseaux d’α-actinine, ainsi que la taille des cardiomyocytes, ont été observés par microscopie. Les observations effectuées montrent que p38γ entraîne une désorganisation des réseaux d’α-actinine lorsqu’il est phosphorylé. Également, il facilite l’hypertrophie des cardiomyocytes en présence de son activateur s’il est forcé hors du noyau ou en l’absence de son motif de liaison aux domaines PDZ. En conclusion, les résultats obtenus suggèrent que p38γ exerce bel et bien un rôle dans le maintien structural des cardiomyocytes par l’intermédiaire de l’α-actinine.
8

Characterization of the Physiological Role of PDZ-RhoGEF in Drosophila and Mice

Jang, Ying-Ju 15 September 2011 (has links)
Biological outputs of insulin/IGF signaling are regulated through essential mediators, such as IRSs, PI3-kinase, and PKB/Akt. These mediators serve critical roles in signal propagation, feedback, and as junctions for crosstalk with other pathways. Abnormal insulin/IGF signaling results in disease, such as obesity, diabetes, and cancer. Given the vital role of this signaling pathway to human health, unraveling its regulatory mechanisms is crucial. Components of this pathway are highly conserved throughout evolution. PTEN, one of the well-defined regulators of this pathway, functions as a lipid phosphatase that negatively regulates insulin/IGF-1 signaling at the PIP3 level, a phosphoinositol that is upregulated by activated PI3-kinase in both Drosophila and mammals. To discover genetic modulators of PTEN in Drosophila, we performed a loss-of-function genetic screen to identify molecules that modify the phenotype elicited by PTEN overexpression in the Drosophila eye. From this screen, we identified a member of the Dbl-family, the guanine nucleotide exchange factor DRhoGEF2, which suppresses the PTEN-overexpression eye phenotype via its effects on dPKB/dAkt activation. By conducting a genetic rescue, we established that PDZ-RhoGEF, a member of the regulator of G-protein signal (RGS)-like domain containing Rho GEFs (RGS-RhoGEFs) subfamily of Dbl-family GEFs, is the mammalian counterpart of DRhoGEF2. PDZ-RhoGEF is essential for cell proliferation and survival through ROCK-dependent activation of IRS/PI3-kinase signaling cascade, which has a major impact on adipose tissue homeostasis. Through an integrative approach, we have demonstrated that DRhoGEF2/PDZ-RhoGEF-dependent signaling has tissue-specific effects on insulin/IGF-signaling throughput in both Drosophila and mammals. Particularly, we have demonstrated the role played by PDZ-RhoGEF in diet related pathology, provides an alternative therapeutic opportunity in disease intervention.
9

The impact of the syndecan-PDZ interactome on endosomal trafficking and extracellular vesicle composition / L'impact de l'interaction syndecan-PDZ sur le trafic endosomal et la composition des vésicules extracellulaires

Castro Cruz, Monica del Carmen 19 July 2018 (has links)
Les syndécans forment une famille de quatre protéines transmembranaires qui sont substituées par l'héparane sulfate. Grâce à ces chaînes glucidiques extracellulaires, les syndécans contrôlent la signalisation d'une pléthore de facteurs de croissance et de molécules d'adhésion. Une autre caractéristique remarquable des syndécans est la conservation de leur domaine intracellulaire au cours de l'évolution. Ce domaine contient un motif C-terminal qui peut induire une interaction avec les protéines dites «PDZ». Les interactions PDZ sont promiscues et les protéines PDZ contrôlent divers aspects de la signalisation cellulaire et de la communication cellule-cellule. Quatre interactions syndecan-PDZ ont été décrites à ce jour et toutes ces interactions ont des effets drastiques sur le comportement des cellules. En particulier, il a été documenté que l'interaction syndécan-synténine a un impact sur le trafic intracellulaire de molécules de signalisation liant l’héparan sulfate. De plus, les syndécans et la synténine coopèrent dans le contrôle la biogenèse des exosomes, organites extracellulaires fonctionnant comme des médiateurs importants de la communication cellule-cellule (y compris dans différentes maladies systémiques comme le cancer). Le protéome humain compte 150 protéines PDZ qui contiennent 266 domaines PDZ. Dans ce travail, nous avons mis à jour la complexité de l'interactome syndecan-PDZ et testé son impact sur le trafic membranaire et sur la composition des vésicules extracellulaires. Notre travail ouvre la voie à une meilleure compréhension des réseaux moléculaires contrôlant la communication cellule-cellule en physio-pathologie. / Syndecans form a family of four transmembrane proteins that are substituted with heparan sulfate. By virtue of these extracellular carbohydrate chains, syndecans control the signaling of a plethora of growth factors and adhesion molecules. Another remarkable feature of syndecans is the conservation of their intracellular domain through evolution. This domain contains a C-terminal motif that can mediate interaction with PDZ proteins. PDZ interactions are promiscuous and PDZ proteins control various aspects of cell signaling and cell-cell communication. Four syndecan-PDZ interactions have been described so far and all these interactions have broad effects on cell behavior. In particular, it was documented that syndecan-syntenin interaction has impact on the intracellular trafficking of heparan sulfate cargo. Moreover syndecan-syntenin controls the biogenesis of exosomes, extracellular organelles emerging as important mediators of cell-cell communication in health and diseases. The human proteome contains 150 PDZ proteins and 266 PDZ domains. Here we started addressing the complexity of the syndecan-PDZ interactome and tested for its impact on membrane trafficking and on the composition of extracellular vesicles. Our work paves the way for a better understanding of the molecular mechanisms and networks controlling cell-cell communication in health and disease.
10

Καθορισμός πρωτεϊνικών αλληλεπιδράσεων δεσμίνης και άλλων πρωτεϊνών

Βλάχου, Θεοδώρα-Ευανθία 30 July 2007 (has links)
Η ΒΥΠ διαθέτει αντίτυπο της διατριβής σε έντυπη μορφή στο βιβλιοστάσιο διδακτορικών διατριβών που βρίσκεται στο ισόγειο του κτιρίου της. / Η δεσμίνη, το μυοειδικό μέλος της οικογένειας των ενδιάμεσων ινιδίων, εκφράζεται σε καρδιακό, γραμμωτό και λείο μυ. Στις ώριμες γραμμωτές μυϊκές ίνες, το δίκτυο των ενδιάμεσων ινιδίων δεσμίνης περιβάλλει τους Ζ-δίσκους, ενώνοντας τον ένα με τον άλλο και φαίνεται να συνδέει ολόκληρη τη συσταλτή συσκευή με το σαρκείλημμα, διάφορα μεμβρανώδη οργανίδια και τον πυρήνα. Σε μια προσπάθεια να κατανοηθεί η μοριακή φύση αυτών των αλληλεπιδράσεων, το εργαστήριο ξεκίνησε έναν έλεγχο χρησιμοποιώντας το σύστημα διπλού υβριδίου ζύμης, χρησιμοποιώντας διαφορετικά τμήματα της δεσμίνης, συμπεριλαμβανόμενων των περιοχών της κεφαλής και της ουράς του μορίου. Χρησιμοποιώντας την περιοχή του Ν-τελικού άκρου της δεσμίνης, βρέθηκαν αρκετές πιθανές πρωτεΐνικές αλληλεπιδράσεις. Αυτές περιλάμβαναν τη Smp3 mannosyltransferase, μια πρωτεΐνη με PDZ περιοχές και την prosaposin. Η Smp3 mannosyltransferase προσθέτει την 4η μαννόζη στη φωσφατιδυλοϊνοσιτόλη κατά τη μετα-μεταφραστική τροποποίηση των γλυκοζυλοφωσφτιδυλοϊνοσιτολίων (GPIs). Η πρωτεΐνη με PDZ περιοχές (η οποία φαίνεται να είναι η MUPP1) περιέχει 13 PDZ περιοχές και είναι γνωστό ότι συνδέει τις διαμεμβρανικές περιοχές των στενοσυνδέσμων με ενδοκυττάρια μηνυματοφόρα μόρια. Η prosaposin είναι μια γλυκοπρωτεΐνη 511 αμινοξέων, η οποία αποτελεί πρόδρομο μόριο για τις τέσσερις saposins (sphingolipid activator proteins A, B, C, D). Ο σκοπός της παρούσας διπλωματικής εργασίας είναι η επιβεβαίωση των αλληλεπιδράσεων αυτών και η περαιτέρω μελέτη της πιο σημαντικής. Χρησιμοποιώντας τη μέθοδο GST pull down βρέθηκε ότι το αμινοτελικό άκρο της δεσμίνης όντως αλληλεπιδρά με την Smp3 mannosyltransferase, την πρωτεΐνη PDZ και την prosaposin. Περαιτέρω ανάλυση με την prosaposin έδειξε ότι το αμινοτελικό άκρο της δεσμίνης αλληλεπιδρά με το τμήμα της prosaposin που αντιστοιχεί στη saposin D και όχι με το καρβοξυτελικό άκρο της prosaposin, το οποίο περιέχει μια saposin-like περιοχή. Τα παραπάνω αποτελέσματα αν επιβεβαιωθούν in vivo, προτείνουν έναν πιθανό ρόλο της δεσμίνης στη συγκρότηση πρωτεϊνικών συμπλόκων, τον έλεγχο της αναγέννησης και ανακύκλωσης μεμβρανών, τη μεταγωγή σήματος, το μεταβολισμό των λιπιδίων και τη μεταφορά στα υποκυτταρικά οργανίδια. / Desmin, the muscle-specific member of the intermediate filaments family, is expressed in cardiac, skeletal and smooth muscle. In the mature striated myofibrils, the network of desmin intermediate filaments surrounds Z-discs, extends from one Z-disc to the other and seems to associate with the nucleus, the plasma membrane and other membranous organelles, including mitochondria and sarcoplasmic reticulum. In an effort to understand the molecular nature of these interactions, the laboratory has started a global yeast two-hybrid screen using different desmin fragments, including the head and tail domains of the molecule. Using the desmin N-terminal domain, several potential interacting proteins were found. These include prosaposin, a protein with PDZ domains and Smp3 mannosyltransferase. Smp3 mannosyltransferase adds the 4th mannose to phosphatidyloinositol during the post-translation modification of GPIs. The protein with PDZ domains, which seems to be MUPP1, has 13 PDZ domains and is known to connect the transmembrane domains of the tight junctions with messenger molecules. Prosaposin is a glycoprotein with 511 amino acids, which is cleaved in four mature saposins (sphingolipid activator proteins), when it reaches the lysosomes. The purpose of this work is to verify these interactions and further study the most important one. Using the GST pull down assays, it was verified that the amino terminus of desmin interacts indeed with Smp3 mannosyltransferase, protein PDZ and prosaposin. Further analysis with prosaposin demonstrated that the amino terminus of desmin interacts with the part of prosaposin that corresponds to saposin D and not with the downstream carboxy terminus of prosaposin that contains a saposin-like domain. All the above data, if verified in vivo could suggest a possible role of desmin in the assembly and stabilization of protein-complexes, in the control of biogenesis and regeneration of membranes, in signal transduction, in lipid metabolism and trafficking towards subcellular organelles.

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