5 mutations responsables de retard mental ont été identifiées dans le gène p21-activated kinase 3 (pak3). Nous avons récemment identifiés dans pak3 deux exons alternatifs très conservés appelés b et c. Ainsi, en plus du variants PAK3a (dépourvu des inserts b ou c), le gène pak3 code pour 3 nouveaux variants d’épissage PAK3b, PAK3c et PAK3cb qui sont constitutivement actifs et insensibles aux GTPases. De plus, contrairement à PAK1 et PAK3a, leur domaine d’auto-inhibition est incapable d’inhiber un domaine kinase. Ainsi, le but de ce projet était de comprendre le mécanisme de régulation de la kinase PAK3. Un modèle de régulation a récemment été proposé dans lequel PAK1 forme des homodimères pouvant être dissociés par les GTPases, permettant ainsi l’activation de la kinase. En se basant sur ces observations j’ai cherché à identifier les dimères PAK3 et j’ai montré que les kinases PAK3a, b, c et cb forment préférentiellement des hétérodimères avec PAK1. J’ai démontré l’existence de ces dimères dans le cerveau et j’ai mis en évidence que ces hétérodimères permettent à chaque monomère de réguler l’activité kinase de son partenaire in vitro. Ce travail permet de proposer un modèle de régulation symétrique pour PAK3a qui forme des hétérodimères avec PAK1 et un nouveau modèle de régulation asymétrique pour les variants d’épissage, également basé sur leur hétérodimérisation avec PAK1. Mes résultats montrant une corégulation des kinases PAK neuronales suggèrent d'une part que leur activation puisse être synchronisée et d'autre part que dans certaines situations physiopathologiques (Cancer et maladies neurologiques) leur dérèglement puissent interférer. / 5 mutations responsible for mental retardation have been identified in p21-activated kinase 3 (pak3) gene. We recently identified in pak3, two highly conserved alternative exons called b and c. In addition to the classical PAK3a variant (without any alternative exon), the pak3 gene encodes 3 new splice variants PAK3b, PAK3c and PAK3cb which are constitutively active and insensitive to GTPase activation. Moreover, unlike PAK1 or PAK3a, their autoinhibitory domain is unable to inhibit a kinase domain. The aim of this project was to understand how PAK3 regulation occurs. A model of regulation was recently proposed in which PAK1 forms homodimers that can be dissociated through GTPase binding, leading to kinase activation. Given these observations, I searched to identify PAK3 dimers and I showed that PAK3a, b, c and cb preferentially form heterodimers with PAK1. I demonstrated the existence of such dimers in the brain and that the different heterodimers allow each monomer to regulate the kinase activity of its partner. Through this study, I propose a symmetric regulation model for PAK3a which heterodimerizes with PAK1 and a new asymmetric regulation model for splice variants, also based on heterodimerization with PAK1. My results showing a co-regulation of neuronal PAK kinases suggest that their activation may be synchronized but also that, in some physiopathological situations (cancers and neurologic diseases), their misregulation may interfere.

Les gliomes sont les tumeurs cérébrales les plus fréquentes chez l’adulte. Il s’agit d’un groupe de tumeurs hétérogène pouvant être classées dans différents sous-groupes selon des critères moléculaires et histopathologiques, donnant une indication sur leur agressivité. Les p21-activated kinase (PAK) sont des sérine-thréonine kinases effectrices des GTPases Rac et Cdc42 et font ainsi partie de nombreuses voies de signalisation. Elles régulent de nombreuses voies d’intérêt dans la biologie des cancers, comme les voies Mek/Erk, PI3K/Akt et Wnt/b-caténine. PAK1 est fréquemment surexprimé et/ou suractivé dans plusieurs cancers, notamment du sein, des ovaires de la prostate et du cerveau, alors que PAK3 induit la sortie du cycle cellulaire et la différenciation des cellules au cours de la neurogenèse dans plusieurs modèles animaux. Durant ma thèse, j’ai pu observer que l’expression de PAK3 était de bon pronostic pour les patients atteints de gliomes, et était plus élevée dans un sous-type de tumeurs caractérisé par la codélétion 1p/19q. In vitro, l’expression de PAK3 était plus élevée dans une lignée de cellules de gliome de signature proneurale, non tumorigène après xenogreffe chez la souris. Au cours de la différenciation des cellules de gliome, l’augmentation de l’expression de PAK3 est associée avec des marqueurs de lignage neural et neuronal. L’inhibition de l’expression de PAK3 entraîne l’augmentation de la capacité d’auto-renouvellement et de la tumorigénicité d’une lignée de cellules de gliome, et favorise la différenciation gliale des cellules. / Gliomas are the most common and lethal adult primary brain tumors. Their complex heterogeneity is evidenced by numerous genomic studies showing distinct molecular entities in glioma. P21-activated-kinases (PAK) are serine threonine kinases involved in multiple signal transduction pathways as downstream effectors of Rac and Cdc42. They regulate several key cancer-relevant pathways like cell division and movement. PAK1 and PAK3 are highly expressed in the brain; PAK1 is frequently overexpressed and/or over-activated in several human cancers whereas PAK3 is involved in neural differentiation and the developmental proneural pathway. The role of these two kinases in brain tumor pathophysiology is unknown. We have observed that PAK3 expression was associated with a longer survival for patients with glioma and was higher in 1p/19q gliomas. In vitro, PAK3 was highly expressed in a glioma cell line with a proneural signature that did not induce tumor after xenograft. Its increasing expression upon a set of differentiation paradigms was correlated with those of neural and/or neuronal markers in glioma cell lines. Inhibition of PAK3 expression increased cell renewal and tumorigenicity. It impaired cell differentiation, promoting the glial lineage.

Indiana University-Purdue University Indianapolis (IUPUI) / Neurofibromatosis type 2 (NF2) is an autosomal dominant cancer predisposition in which loss of heterozygosity at the NF2 gene locus leads to the development of tumors of neural crest derived origin, most commonly bilateral vestibular schwannomas. There are currently no FDA approved chemotherapeutic agents for treatment in patients with NF2. Development of therapeutic agents has been hampered by our incomplete knowledge of how Merlin, the protein product of the NF2 gene, functions as a tumor suppressor. In order develop a deeper understanding for how loss of Merlin leads to oncogenic transformation in Schwann cells we have developed a genetically engineered mouse model (GEMM) of Neurofibromatosis Type 2 in which functional expression of Merlin is lost in Schwann cell precursors. In parallel studies utilizing these mice, we have sought to understand the pathophysiology driving tumor formation in Merlin deficient Schwann cells. In Chapter 1, we explore the role of Merlin as a negative regulator of the Group A p21 activated kinases, PAK1 and PAK2. We demonstrate that PAK1, a previously well established oncogene in solid tumors and Merlin binding partner, is hyperactivated in Merlin deficient schwannomas. Through therapeutic interventions and genetic manipulations we demonstrate that inhibition of PAK1 was capable of reducing tumor formation and alleviating sensorineural hearing loss in our NF2 GEMM. In Chapter 2, we investigate the role of NF-kB inducing kinase (NIK) and NF-kB signaling in the formation and growth of Merlin deficient Schwann cell tumors. Prior work in our lab as well as by others demonstrated elevated NF-kB signaling in Merlin deficient Schwann cell tumors. We observed accumulation of a catalytically active fragment of NF-kB inducing kinase and present data that accumulation of a 55Kd constitutively active fragment of NIK is sufficient trigger wild type Schwann cells to form tumors. In vivo however, Schwann cell intrinsic expression of NIK is not required for tumor formation or growth. / 2 years (2021-05-24)

5 mutations responsables de retard mental ont été identifiées dans le gène p21-activated kinase 3 (pak3). Nous avons récemment identifiés dans pak3 deux exons alternatifs très conservés appelés b et c. Ainsi, en plus du variants PAK3a (dépourvu des inserts b ou c), le gène pak3 code pour 3 nouveaux variants d'épissage PAK3b, PAK3c et PAK3cb qui sont constitutivement actifs et insensibles aux GTPases. De plus, contrairement à PAK1 et PAK3a, leur domaine d'auto-inhibition est incapable d'inhiber un domaine kinase. Ainsi, le but de ce projet était de comprendre le mécanisme de régulation de la kinase PAK3. Un modèle de régulation a récemment été proposé dans lequel PAK1 forme des homodimères pouvant être dissociés par les GTPases, permettant ainsi l'activation de la kinase. En se basant sur ces observations j'ai cherché à identifier les dimères PAK3 et j'ai montré que les kinases PAK3a, b, c et cb forment préférentiellement des hétérodimères avec PAK1. J'ai démontré l'existence de ces dimères dans le cerveau et j'ai mis en évidence que ces hétérodimères permettent à chaque monomère de réguler l'activité kinase de son partenaire in vitro. Ce travail permet de proposer un modèle de régulation symétrique pour PAK3a qui forme des hétérodimères avec PAK1 et un nouveau modèle de régulation asymétrique pour les variants d'épissage, également basé sur leur hétérodimérisation avec PAK1. Mes résultats montrant une corégulation des kinases PAK neuronales suggèrent d'une part que leur activation puisse être synchronisée et d'autre part que dans certaines situations physiopathologiques (Cancer et maladies neurologiques) leur dérèglement puissent interférer.

The common type of myxoid soft tissue sarcomas is myxofibrosarcoma. Clinically, increased tumor grading and staging are frequently observed in myxofibrosarcomas after relentless local recurrences, which may eventually lead to metastatic diseases. However, metastatic myxofibrosarcomas are often refractory to current treatment strategies and constitute the primary cause of sarcoma-related death. Immunohistochemistry staining was applied to analyze myxoid tumors of soft tissue in our previous studies, and p21 protein (Cdc42/Rac)-activated kinase 1 (PAK1) was identified to be significantly upregulated in myxoid soft tissue sarcomas. The PAK1 is a pivotal serine/threonine kinase, which integrates stimuli from various signaling pathways to regulate cell survival, mitosis and cytoskeletal remodeling, etc. We first examined the endogenous PAK1 mRNA and total PAK1 protein levels in various myxoid sarcoma cell lines, including OH931, NMFH1 and NMFH2. This initial screening detected that upregulated PAK1 expression in OH931 and NMFH1, whereas downregulated PAK1 in NMFH2 cells. By wound healing and matrigel transwell assay, we further found that transfection of the expression plasmid carrying wild-type PAK1 gene or PAK1 T423E mutant promoted cell migration and invasion abilities in NMFH2 cells. On the other hand, knockdown of the PAK1 gene by short hairpin RNA interference inhibited the migration rate and invasion ability in NMFH1 cells. By 5-bromo-2-deoxyuridine assay and colony formation assay, we found that either exogenous expression of PAK1 protein or knockdown of PAK1 gene affected cell proliferation and transformation. Interestingly, immunofluorescence demonstrated that treatment with hepatocyte growth factor induced phosphorylation of PAK1 (Thr212) and promoted its nuclear import in NMFH2 cells. In summary, PAK1 plays oncogenic roles in myxoid sarcoma carcinogenesis.

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<p>Glomerulosclerosis (GS) is the irreversible scarring of glomerular tissue which underlies the development of chronic kidney disease (CKD). Increased intraglomerular capillary pressure (P_gc) is a major contributor to the development of GS and can occur in both hypertensive and diabetic patients. With elevated P_gc, <em>in vitro</em> and <em>in vivo</em> evidence suggest that mesangial cells (MC) experience cyclic stretch and secrete pro-fibrotic factors such as connective tissue growth factor (CTGF) which contributes to GS. The signaling pathways that are activated in response to elevated P_gc and lead to extracellular matrix (ECM) production in MCs are the main focus of this thesis.</p> <p>Previous data demonstrated activation of the Rho GTPase, Rac1, with cyclic stretch in MCs. Furthermore, the most characterized effector of Rac1, p21-activated kinase (PAK), has been observed to have a role in endothelial cells (ECs) exposed to mechanical stress. We thus proposed that the Rac1-PAK signaling pathway is involved in mechanical stress signaling in MCs.</p> <p>Our data demonstrate that Rac1-PAK signaling was activated in response to cyclic stretch and required for stretch-induced CTGF production in MCs. RhoA activation was also regulated by Rac1-PAK signaling, and RhoA/ROCK were observed to mediate CTGF upregulation with stretch. Further investigation on the role of Rac1-PAK signaling and how it regulates CTGF in MCs exposed to stretch, will provide insight into potential therapeutic targets to delay the progression of hypertension-mediated CKD.</p> / Master of Science in Medical Sciences (MSMS)

The important factor in regulation of metabolic processes is regulatory proteins, which are able to react by feed-back to energetic state of the cell. Big attention is focused on the AMP activated kinase (AMPK) and NAD+ activated deacetylase SIRT1. These enzymes interact together and their stimulation increases mitochondrial biogenesis and fatty acid oxidation. Due to this it functions beneficially against the onset of obesity, insulin resistance and ageing. Fasting, exercise and some antidiabetogenic drugs act by these regulators. n-3 polyunsaturated fatty acids (PUFA) are also known because of their stimulative effects on mitochondrial biogenesis and -oxidation. Previous work of our group have showed that intake of higher dose of n-3 polyunsaturated fatty acids (PUFA) in diet lead to increase in activity of AMPK in white adipose tissue. New results presented in this thesis show that SIRT1 is essential for increase in expression of stimulators of -oxidation (PPAR etc) in response to n-3 PUFA in diet. n-3 PUFA futher improve the metabolic profile synergistically with calorie restriction probably through SIRT1.

Objetivamos investigar o papel da quinase ativada por adenosina monofosfato (AMPK) na doença renal crônica. Induzimos nefrite túbulo-intersticial (NTI) em camundongos C57BL/6 e LyzM-cre AMPKflox/flox através de ração com adenina, e tratamos com metformina (Met) 200 mg/kg/dia. Avaliamos ainda o efeito da Met sobre a transição epitélio-mesenquimal (TEM) em células tubulares epiteliais renais murinas (linhagem MM55.K). Os C57BL/6 tratados apresentaram preservação da função renal; maior frequência de macrófagos (MØ) M1, em detrimento dos M2; e redução de marcadores de fibrose. Os LyzM-cre AMPK-/- não diferiram dos LyzM-cre AMPK+/+ quanto à intensidade da lesão, por a molécula já se encontrar infrarregulada na NTI. Contudo, ao serem tratados com Met, os LyzM-cre AMPK+/+ evoluíram melhor do que os não tratados, o mesmo não se verificando nos LyzM-cre AMPK-/-, sugerindo que a ação da Met nos MØ é dependente de AMPK. As MM55.K, após estímulo com Met, exibiram maior captação de glicose, expressão do transportador Glut-2, ativação da glicólise, e resistência à TEM. / We aimed to investigate the role of adenosine monophosphate activated kinase (AMPK) on chronic kidney disease. We induced tubulointerstitial nephritis (TIN) in C57BL/6 and LyzM-cre AMPKflox/flox mice by feeding them adenine diet, and then treating with metformin (Met) 200 mg/kg/day. We also evaluated the effect of Met on epithelium-to-mesenchyma transition (EMT) of murine epithelial renal tubular cells (lineage MM55.K). Met-treated C57BL/6 mice presented preserved kidney function, greater frequency of M1 macrophages (MØ) compared to M2 ones, and reduced markers of fibrosis. Disease severity on LyzM-cre AMPK-/- and AMPK+/+ mice did not differ, since the molecule was already downregulated on TIN. However, by treating them with Met, LyzM-cre AMPK+/+ improved in comparison to the non-treated mice. The same did not happen with LyzM-cre AMPK-/- mice, suggesting that Met effect on MØ is AMPK-dependent. MM55.K cells, after stimulus with Met, showed increased glucose uptake, greater expression of the transporter Glut-2, activation of glycolysis, and resistance to EMT.