Master of Science / Biochemistry and Molecular Biophysics Interdepartmental Program / Anna Zolkiewska / Cellular senescence is a state of irreversible cell cycle arrest in response to non-lethal stress. In cancer cells, senescence can be induced by chemotherapy, radiation, or signals from the tumor microenvironment, such as transforming growth factor β (TGFβ). Senescent cells are metabolically active and have altered gene expression compared to their non-senescent counterparts. Senescent cells release a wide variety of factors, including extracellular domains of transmembrane proteins that require proteolytic cleavage by specific proteases. ADAMs (A Disintegrin and Metalloprotease domain-containing proteins) are enzymes that cleave many transmembrane proteins, such as growth factor precursors or adhesion molecules, and thus may act as sheddases in senescent cells. Here, we investigate ADAM expression levels during TGFβ- induced cellular senescence. SUM149PT and SUM102PT breast cancer cells were incubated with TGFβ, followed by treatment with high doses of paclitaxel to remove actively proliferating, non-senescent cells. Induction of cellular senescence was examined by evaluating changes in cell size and granularity, and by β-galactosidase staining. ADAM mRNA levels were measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Among several ADAMs tested, ADAM12 mRNA was significantly upregulated in senescent cells. In addition, we demonstrated that ADAM12 knock-down leads to decreased activation of epidermal growth factor receptor (EGFR), an important modulator of cancer cell growth, survival, and metastasis. This effect of ADAM12 knock-down was likely due to a diminished release of soluble EGF or EGF-like ligands from cells. Since senescent cells often release increased amounts of these ligands, ADAM12 may modulate the senescence secretome in senescent breast cancer cells.

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Le cancer du poumon est un problème majeur de santé publique et dont le coût humain et social est sans cesse en augmentation au cours des dernières années. Parmi les nombreux médiateurs susceptibles de jouer un rôle dans la croissance tumorale, nous avons étudié en détails le système des ADAM et ADAMTS protéases. Les ADAMs sont des enzymes aux fonctionnalités multiples qui interviennent dans de nombreux processus physiologiques et pathologiques. Parmi ces différents processus, certains concernent des modulations de la structure ou de létat de la matrice extracellulaire et dautres des boucles dinteractions entre différents types cellulaires reliés par des médiateurs protéiques. Les modulations apportées à ce système par les ADAM protéases résident donc dans lactivation ou linhibition de certains processus biologiques par clivage de molécules ou activation des récepteurs. Au cours de la première partie de notre travail, nous avons étudié lexpression de différentes ADAM(TS) protéases sélectionnées sur base de la littérature comme potentiellement impliquées dans la régulation de la croissance tumorale. L'analyse d'échantillons de cancers pulmonaires humains a été réalisée en collaboration avec le Professeur P BIREMBAUT (Unité INSERM U 514, Reims). Nous avons mis en évidence que lADAM-12 (forme complète membranaire) est surexprimée et que lADAMTS-1 est moins exprimée dans les tissus tumoraux pulmonaires obtenus par résection chirurgicale par rapport à des échantillons correspondants prélevés en zone saine. Ces variations ont été vérifiées par Real-Time PCR et par western blots. Les niveaux dexpression de lADAM-12 sont corrélés à lexpression des mRNAs codant pour les isoformes 121 et 165 (qui sont pro-angiogènes) du VEGF-A. Une immunohistochimie marquant l'ADAM-12 a montré une expression de cette protéase principalement dans les cellules tumorales ; l'ADAMTS-1 par contre, est surtout exprimée dans le tissu bronchique sain. Les lignées de cellules pulmonaires issues de cellules épithéliales bronchiques et alvéolaires ont été caractérisées pour leur expression en ADAM-12 et ADAMTS-1. LADAM-12 et lADAMTS-1 sont surexprimées par les cellules de type BZR et BZR T33 qui forment des tumeurs chez les souris et qui ont un caractère agressif. Au cours de ces travaux, nous avons donc clairement pu identifier deux protéases dont l'expression est modulée dans nos échantillons de tissu pulmonaire sain ou tumoral. L'ADAM-12, surexprimée dans les tumeurs, serait un modulateur "positif" de la progression tumorale et l'ADAMTS-1, dont lexpression est moindre dans les tumeurs semble être un modulateur négatif du développement tumoral (Rocks et al, Br J Cancer, 2006). Nous avons focalisé la suite de nos travaux sur létude des effets de lADAM-12 et de lADAMTS-1 sur différents phénomènes biologiques impliqués dans la progression tumorale. Sur base de l'analyse des échantillons de cancers pulmonaires, l'ADAM-12 est donc apparue comme un candidat potentiel impliqué dans la progression tumorale. Nous avons ainsi généré des clones surexprimant lADAM-12 à partir de cellules épithéliales bronchiques immortalisées (BEAS-2B). Ces clones ont été caractérisés et leur production dADAM-12 a été démontrée par RT-PCR et cytométrie de flux. Le comportement des cellules surexprimant lADAM-12 a ainsi pu être comparé à celui des cellules parentales transfectées avec le vecteur vide (contenant uniquement le gène de la résistance à la néomycine). Différentes expériences in vitro ont été réalisées sur ces cellules. Il ressort de lensemble de cette caractérisation que les cellules surexprimant lADAM-12 présentent une prolifération et une capacité à former des colonies en agar mou accrues par rapport aux cellules parentales. De plus, les cellules surexprimant lADAM-12 ont une sensibilité vis-à-vis de lapoptose diminuée par rapport aux clones contrôles. Ces processus sont dépendants dune augmentation de la production dHB-EGF mature par les clones surexprimant lADAM-12. Les clones surexprimant lADAM-12 ainsi que les clones contrôle ont été implantés au sein du tissu pulmonaire de souris et injectés dans le tissu sous-cutané. Il ressort de ces expériences que les cellules de type BEAS-2B transfectées ou non par lADAM-12 sont peu tumorigènes qu'elles soient implantées dans un site orthotopique (intra-pulmonaire) ou hétérotopique (sous-cutané) dans les souris SCID. En dépit du fait que l'ADAM-12 stimule la prolifération cellulaire et protège les cellules de lapoptose in vitro, sa surexpression nest pas suffisante en soi pour développer un phénotype tumorigène in vivo (Rocks et al, Cell Prolif, in press). Dans la troisième partie de notre travail, nous avons généré à partir de la lignée dérivée de cellules épithéliales bronchiques tumorales BZR des clones transfectés de façon stable qui surexpriment lADAMTS-1 humaine complète. Ceci est confirmé par la présence de bandes de 87 kDa en Western Blot, représentant la forme complète et active de cette protéase. In vitro, nous navons pas pu mettre en évidence de différence de prolifération, de migration, dinvasion et dapoptose entre les différents clones étudiés. Nous avons ensuite procédé à limplantation au niveau sous cutané dans des souris immunodéficientes de populations cellulaires transfectées de façon stable avec le gène de lADAMTS-1. Nous avons ainsi évalué si la surexpression de cette protéase modifiait le comportement de ces cellules en termes de prolifération in vivo. Les tumeurs formées à partir de cellules transfectées avec la forme complète de lADAMTS-1 présentent une taille plus importante que les tumeurs formées à partir de cellules BZR contrôle. Un immunomarquage pour le Proliferating Cell Nuclear Antigen (PCNA) a révélé des scores de prolifération cellulaire plus élevé dans les tumeurs dérivées de populations cellulaires surexprimant lADAMTS-1. De plus, lanalyse histochimique des tumeurs a montré, dans les tumeurs surexprimant lADAMTS-1, la présence de structures stromales composées de fibronectine (WB), collagène (marquées positivement par coloration au safran, WB) et de myofibroblastes (positifs pour lα-actine des muscles lisses). Afin détudier le potentiel chimiotactique de lADAMTS-1 sur les fibroblastes, nous avons utilisé le modèle des chambres de Boyden. Les chambres du dessous ont été remplies avec des milieux conditionnés dérivés de populations de cellules transfectées ou non avec la forme complète de lADAMTS-1. Les milieux conditionnés de cellules surexprimant lADAMTS-1 ont des capacités dattraction plus importantes sur les fibroblastes que les milieux conditionnés dérivés de cellules contrôles. Cependant, lajout dADAMTS-1 recombinante au milieu conditionné par des cellules contrôles nest pas suffisant pour augmenter la migration des fibroblastes. Nous avons donc mesuré lexpression de facteurs potentiellement impliqués dans le remodelage de la matrice extracellulaire et dans la migration de fibroblastes. Les tumeurs surexprimant lADAMTS-1 ont des taux plus élevés de MMP-13, TGF-β1 et dIL-1β. De plus, un anticorps bloquant les effets du TGF-β1 et/ou de lIL-1β diminue la migration des fibroblastes en chambre de Boyden. En résumé, nous montrons par ce travail, que les cellules BZR transfectées au moyen de la forme complète de lADAMTS-1, forment des tumeurs plus larges, infiltrées par des myofibroblastes, suggérant que les interactions tumeur-stroma influencent la prolifération de cellules tumorales En conclusion, nos travaux ont identifié que lexpression de lADAM-12 et lADAMTS-1 est modulée dans des tumeurs bronchiques humaines. LADAM-12 joue un rôle dans la prolifération cellulaire en activant le clivage de facteurs de croissance membranaires qui sont des ligands de lEGFR. Le rôle de lADAMTS-1 apparaît comme beaucoup plus complexe et nos travaux montrent que lADAMTS-1 peut influencer la croissance tumorale in vivo en modulant la composition cellulaire et matricielle du stroma. Collectivement, ces travaux confirment le rôle clé joué par les protéases de la famille des ADAMs et ADAMTS dans le développement du cancer et identifient ces enzymes comme des cibles thérapeutiques potentielles.

Two key proteins, LexA and RecA, are involved in regulation of the SOS expression system in bacteria. LexA and RecA act as the transcriptional repressor and inducer of the SOS operon, respectively. LexA downregulates the expression of at least 43 unlinked genes and activated RecA interacts with the repressor LexA and therefore, LexA undergoes self-cleavage. The ability of the LexA protein to dimerize is critical for its ability to repress SOS-regulated genes in vivo, as the N-terminal domain (NTD) alone has a lower DNA-binding affinity without the C-terminal domain (CTD) and the components for the dimerization of LexA are located in the CTD. Two antiparallel β-strands (termed β-11) in the CTD at the dimer interface of LexA are involved in the dimerization. LexA interacts with the active form of RecA in vivo during the SOS response. It was determined experimentally that monomeric and non-cleavable LexA binds more tightly to RecA and is resistant to self-cleavage. Therefore, we reasoned that if we can produce such LexA mutants we would be able to stabilize the LexA and active RecA complex for crystallization. Therefore, in this experiment, we attempted to make a non-cleavable and predominantly monomeric LexA that interacts intimately with RecA. We produced four single mutations at the dimer interface of the non-cleavable and NTD-truncated mutant of LexA (∆68LexAK156A) in order to weaken the interactions at the interface. The predominant forms of LexA mutants and the affinities of interaction between the mutant LexA proteins and RecA were examined. ∆68LexAK156AR197P mutant was found as predominantly monomeric at a concentration of 33.3 μM both by gel filtration chromatography and dynamic light scattering (DLS) experiments. It also bound RecA more tightly than wild-type LexA. Another mutant, ∆68LexAK156AI196Y, was also found as predominantly monomeric at a concentration of 33.3 μM by DLS. Both these proteins were subjected to crystallization with wild-type RecA protein. We were able to produce some predominantly monomeric LexA with good binding affinity for RecA; however, we were unsuccessful in co-crystallization.

Gene therapy holds the unprecedented potential to treat disease by manipulating the underlying genetic blueprints of phenotypic behavior. Targeting of gene delivery is essential to achieve specificity for the intended tissue, which is especially critical in cancer gene therapy to avoid destruction of healthy tissue. Adeno-associated virus (AAV) is considered the safest viral vector and, compared to non-viral vectors, offers several advantages: higher efficiency, genetic modification, combinatorial panning, and high monodispersity. Classic viral targeting has focused on engineering ligand-receptor interactions, but many cell surface targets do not support post-binding transduction events. Furthermore, many potential target tissues – such as triple negative breast cancer – may not display a single, unique identifying surface receptor, so new methods of targeting are needed. Alternatively, many pathological states, including most cancers, exhibit upregulation of proteolytic enzymes in the extracellular milieu. The present work describes the development of an AAV platform that has been engineered to activate in response to disease-related proteases. The specificity and sensitivity of these protease-activatable viruses (PAVs) can be tuned to meet the demands of various clinical scenarios, giving the platform some therapeutic versatility. This work represents the first demonstration of a protease-controlled, non-enveloped virus for genetic therapy. These results extend the therapeutic value of AAV, the safest gene vector currently being explored in 73 clinical trials worldwide.

Two key proteins, LexA and RecA, are involved in regulation of the SOS expression system in bacteria. LexA and RecA act as the transcriptional repressor and inducer of the SOS operon, respectively. LexA downregulates the expression of at least 43 unlinked genes and activated RecA interacts with the repressor LexA and therefore, LexA undergoes self-cleavage. The ability of the LexA protein to dimerize is critical for its ability to repress SOS-regulated genes in vivo, as the N-terminal domain (NTD) alone has a lower DNA-binding affinity without the C-terminal domain (CTD) and the components for the dimerization of LexA are located in the CTD. Two antiparallel β-strands (termed β-11) in the CTD at the dimer interface of LexA are involved in the dimerization. LexA interacts with the active form of RecA in vivo during the SOS response. It was determined experimentally that monomeric and non-cleavable LexA binds more tightly to RecA and is resistant to self-cleavage. Therefore, we reasoned that if we can produce such LexA mutants we would be able to stabilize the LexA and active RecA complex for crystallization. Therefore, in this experiment, we attempted to make a non-cleavable and predominantly monomeric LexA that interacts intimately with RecA. We produced four single mutations at the dimer interface of the non-cleavable and NTD-truncated mutant of LexA (∆68LexAK156A) in order to weaken the interactions at the interface. The predominant forms of LexA mutants and the affinities of interaction between the mutant LexA proteins and RecA were examined. ∆68LexAK156AR197P mutant was found as predominantly monomeric at a concentration of 33.3 μM both by gel filtration chromatography and dynamic light scattering (DLS) experiments. It also bound RecA more tightly than wild-type LexA. Another mutant, ∆68LexAK156AI196Y, was also found as predominantly monomeric at a concentration of 33.3 μM by DLS. Both these proteins were subjected to crystallization with wild-type RecA protein. We were able to produce some predominantly monomeric LexA with good binding affinity for RecA; however, we were unsuccessful in co-crystallization.

Human T-cell lymphotropic virus type I (HTLV-I) is a retrovirus that is the causative agent of the fatal disease adult T-cell leukemia (ATL). HTLV-I silently infects over twenty million people worldwide; up to ten percent of these will develop ATL in their lifetime. There are currently no effective treatments for this disease. HTLV-I expresses its genome as polypeptides that must be processed in order to produce infectious virions. Like other retroviruses, HTLV-I encodes an aspartic acid protease to process these polypeptides into mature form. Because the protease is essential in the virus life cycle, it is an attractive target for the treatment of HTLV-I-induced ATL. The present work examines the structure and function of HTLV-I protease. A theoretical structure of the protease is presented, and the function of the C-terminal extension is considered. In order to determine which residues are involved in binding substrate, two experiments were performed: first, several residues were mutated to the corresponding residues in HIV-1 protease to determine whether HTLV-I protease can be made to process an HIV-1 protease substrate; second, an alanine scan was performed to knock out individual residues to assess their importance in binding substrate. This work builds knowledge of the structure and function of HTLV-I protease. By understanding which residues play a role in binding substrate and by developing a clearer picture of the structure of the protease, it will be possible to develop specific inhibitors for HTLV-I protease.

G-NNACI, a Naja naja atra chymotrypsin inhibitor consists of 57 amino acid residues cross-linked by three disulfide bridges and belongs to the Kunitz/BPTI superfamily, has been successfully cloned and expressed in our laboratory. Since snake venom non-neurotoxic Kunitz/BPTI inhibitors are most conserved in the core and in the N-terminal surface area, Ala-screening mutagenesis, deletion and Domain swapping on the N-terminus were carried out in this study to assess the role of N-terminus in G-NNACI. G-NNACI mutants with single amino acid substitution and deleted mutants were prepared. The secondary structure of all mutated proteins did not significantly alter as evidenced by CD spectra. Although all mutants are found to be functionally active as an inhibitor, their inhibitory potency against chymotrypsin differed. In contrast to G-NNACI and other mutants, R1A¡BP2A and ¡µN3 mutants had a propensity to alter their disulfide linkages under basic conditions. The results of thermal and urea denaturation suggested that amino acid substitution and deletion at the N-terminus lead to a change in the structural stability of G-NNACI. Consequently, the inhibitory potency of G-NNACI mutants along with time was affected. B chain of

This study has investigated the gene expression of ubiquitin¡B20S proteasome beta subunit type 1 (20s£]1)¡Bubiquitin-conjugating enzyme e2 (ucee2)¡BATP-dependent caseinolytic protease regulatory subunit (clpC) in the marine macroalga Ulva fasciata Delile in relation to the hypersalinity-induced oxidative stress and protein oxidation. During the early stage (0-1 h), the water contents and TTC (2,3,5-tripheny tetrazolium chloride) reduction ability maintained unchanged but recovery ability and photosynthetic ability (PS II activity as indicated by Fv/Fm) were decreased along with accumulated H2O2, suggesting the occurrence of oxidative stress. Only ubiquitin expressed at this stage. During 1-3 h, water lost (approximately 33% of the control) with a further decrease in recovery ability, TTC reduction ability¡BPS II activity but more H2O2 accumulation and protein carbonyl compound. The transcripts of 20s£]1 and clpC and caseinolytic protease activity increased at this stage with the maximum of clpC at hour 3. In the 6-48 h, water lost seriously with high accumulated free amino acid at 6-12 h but low recovery ability. The transcript amounts of ubiquitin¡B20s£]1 and ucee2 increased marked during this stage, in which these might be related to programmed cell death caused by long-term exposure to hypersalinity. Reactive oxygen species (ROS) scavengers inhibited H2O2 accumulation, caseinolytic proteolytic activity increase, carbonyl compound formation and gene expression of ubiquitin¡B20s£]1¡Bucee2¡BclpC, indicating a role of ROS in the regulation of protease genes. A role of polyamines in the regulation of protease gene expression was tested. Spermidine and spermine inhibited the gene expression of ubiquitin¡B20s£]1 and ucee2, the oxidation of proteins (carbonyl groups) and the induction of caseinolytic protease activity in 90‰-treated thalli, whereas putrescine inhibited clpC expression, the oxidation of proteins and caseinolytic protease activity but enhanced the gene expression of ubiquitin¡B20s£]1 and ucee2. In conclusion, the results of the present investigation show that the degradation of oxidatively damaged proteins under hypersalinity conditions by increased caseinolytic protease activity is driven by the up-regulation of clpC gene expression via ROS and polyamines. It seems likely that the induction of ubiquitin¡B20s£]1 and ucee2 gene expression might be associated with the hypersalinity-mediated programmed cell death.