abstract: Engineered nanoparticles (NP; 10-9 m) have found use in a variety of consumer goods and medical devices because of the unique changes in material properties that occur when synthesized on the nanoscale. Although many definitions for nanoparticle exist, from the perspective of size, nanoparticle is defined as particles with diameters less than 100 nm in any external dimension. Examples of their use include titanium dioxide added as a pigment in products intended to be ingested by humans, silicon dioxide NPs are used in foods as an anticaking agent, and gold or iron oxide NPs can be used as vectors for drug delivery or contrast agents for specialized medical imaging. Although the intended use of these NPs is often to improve human health, it has come to the attention of investigators that NPs can have unintended or even detrimental effects on the organism. This work describes one such unintended effect of NP exposure from the perspective of exposure via the oral route. First, this Dissertation will explain an event referred to as brush border disruption that occurred after nanoparticles interacted with an in vitro model of the human intestinal epithelium. Second, this Dissertation will identify and characterize several consumer goods that were shown to contain titanium dioxide that are intended to be ingested. Third, this Dissertation shows that sedimentation due to gravity does not artifactually result in disruption of brush borders as a consequence of exposure to food grade titanium dioxide in vitro. Finally, this Dissertation will demonstrate that iron oxide nanoparticles elicited similar effects after exposure to an in vitro brush border expressing model of the human placenta. Together, these data suggest that brush border disruption is not an artifact of the material/cell culture model, but instead represents a bona fide biological response as a result of exposure to nanomaterial. / Dissertation/Thesis / Doctoral Dissertation Biology 2014

No description available.

Die Plasmamembranspannung von eukaryotischen Zellen soll maßgeblich zur Regulation von zellulären Prozessen wie der Zellmigration, Mitose, Endo- und Exozytose, Membranreparatur, Osmoregulierung und Zellspreiten beitragen, welche zu einer Veränderung der Membranfläche und ihrer Deformation führt. In dieser Arbeit wurde die epitheliale Zelllinie MDCK II (Madin-Darby Canine Kidney) benutzt, um spannungsgesteuerte Oberflächenregulierung zu untersuchen. Indentationsexperimente kombiniert mit dem Herausziehen von Membrannanoröhren wurden mit Hilfe des Rasterkraftmikroskops (Atomic Force Microskope, AFM) durchgeführt, um lokale Variationen in der Membranspannung und überschüssiger Membranfläche als Funktion von äußeren Reizen abzuschätzen. Die verwendeten externen Stimuli beinhalten eine Veränderung der Funktionalität des Actomyosin-Cortexes durch die Wirkung von Blebbistatin und Cytochalasin D, sowie die Manipulation der Zytoskelett-Membran Adhäsionspunkte durch Einzel-Mikroinjektion. Die Injektion von Neomycin verhindert die Anbindung von ERM-Proteinen an das Lipid Phosphatidylinositol-(4,5)-bisphosphat (PIP2) und bewirkt somit die Abkopplung des Zytoskeletts von der Plasmamembran. Als Gegenexperiment diente die Injektion des Lipids PIP2 selbst, welches zur Erhöhung der Anzahl der Zytoskelett-Membran Adhäsionspunkte führte. Weiterhin wurden die als Membranreservoire dienenden Mikrovilli durch den Entzug von Cholesterol entfernt. Auswirkung auf das Vorhandensein von Membranreservoiren hat ebenfalls die Veränderung des osmotischen Drucks innerhalb der Zellen. Zusätzlich wurden die elastischen Eigenschaften von apikalen Zellmembran-Fragmenten von konfluenten MDCK II Zellen untersucht, welche Aufschluss über die intrinsischen Membraneigenschaften ohne den Einfluss des Zytosols und Zytoskeletts geben konnten. Abschließend wurde die Mechanik von adhärierenden und spreitenden Zellen untersucht. Zusammenfassend kann gesagt werden, dass die Plasmamembran, bestehend aus einer Phospholipiddoppelschicht, lateral schwer ausdehnbar ist aufgrund ihrer flüssig-kristallinen Natur. Durch das Vorhandensein von dynamischen Membranreservoiren wie Mikrovilli, die schnell auf Veränderungen der Membranspannung durch Membranhomöostase reagieren, werden zellulare Prozesse wie die Zellmotilität oder die Anpassung an osmotischen Stress ermöglicht. In der vorliegenden Arbeit gelang es gleichzeitig, die Membranspannung und die Verfügbarkeit von Membranfläche von adhärenten konfluenten als auch von adhärierenden und spreiten Zellen zu messen. Die durchgeführten Experimente ergaben ein detailliertes Bild wie sich die zelluläre Oberflächenregulierung in der Membranmechanik widerspiegelt.

Made available in DSpace on 2014-06-11T19:23:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-04-26Bitstream added on 2014-06-13T20:11:19Z : No. of bitstreams: 1 trujillopiso_dy_me_jabo.pdf: 568286 bytes, checksum: b44892a30feb375528cce6058638d8cb (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Estudaram-se os efeitos do sulfato de condroitina 3% (SC), da N-acetilcisteína 10% (NAC), do EDTA 1% (EDTA) e solução salina (GC), sobre a viabilidade do epitélio corneal e a concentração de metaloproteinases (MMP-2 e MMP-9), em córneas de ratos submetidos à ulceração química por NaOH 1N. Compuseram-se quatro grupos de vinte e quatro animais, que foram submetidos à queimadura química corneal com NaOH 1N. Os tratamentos foram realizados a intervalos de 6 horas e as córneas fotografadas, nos mesmos períodos, após tingimento com fluoresceína, até a reepitelização. Doze animais de cada grupo foram submetidos à eutanásia humanitaria, 20 horas após ulcerações. O mesmo procedimento foi repetido às 42 horas para os outros doze animais de cada grupo. As córneas foram processadas para quantificação de microvilosidades do epitelio corneal por microscopia eletrônica de varredura e para quantificação da MMP-2 e -9, por zimografia. O tempo médio de epitelização em horas foi de 28,00±12,82 (SC), 29,00±11,01 (NAC), 35,00±7,01 (EDTA) e de 35,00±7,01 (GC), sem diferença signficativa (p=0,46) entre os grupos. Não se observou diferença quanto ao número de MEC entre os grupos (p>0,05). Às 20 e às 42 horas, a forma latente da MMP-2 foi significativamente mais elevada nos grupos NAC e SC (p<0,001), e às 42 horas observou-se maior concentração em EDTA, relativamente ao GC (p<0,001). Às 42 horas, a concentração da MMP-2, em sua forma ativa, foi significativamente maior, no grupo SC, relativamente aos demais grupos (p<0,001). A MMP-9 só se expressou em sua forma latente, sendo sua concentração significativamente mais elevada, no grupo NAC, às 42 horas (p<0,001). Concluiu-se, que das substâncias testadas, só o sulfato de condroitina acelerou a epitelização corneal, mas nenhuma delas apresentou efeitos protetores às microvilosidades do epitélio corneal... / This study aimed evaluate the effects of topical 3% chondroitin sulfate (SC), 10% N-acetylcysteine (NAC), 1% EDTA (EDTA) and 0,9% NaCl on corneal epithelial viability and the expression of matrix metalloproteinase-2 and -9 (MMP-2 and -9), in alkali burned rat corneas. Ninety eight healthy rats were divided into four groups and animals were submitted to corneal burn with NaOH 1N. All treatments occurred every 6 hours, and the corneas were photographed at the same time points until lesions were fluorescein negative. Twelve animals of each group were euthanized 24 and 42 hours after burn, and corneas were processed for corneal epithelial microvilli quantification (CEM) by scanning electron microscopy and MMP-2 and -9 evaluation by zimography. Images were quantified by Image J. Average corneal wound healing rate was 28,00±12,82 (SC), 29,00±11,01 (NAC), 35,00±7,01 (EDTA) and 35,00±7,01 hours in controls (GC) (p=0,46). CEM count did not change significantly among groups (p>0,05). At 20 and 42 hours, MMP-2 latent form quantity was significantly increased in NAC and SC groups (p<0.001); at 42 hours, MMP-2 latent form was significantly elevated in EDTA, in comparison to GC (p<0,001). At 42 hours, MMP-2 active form was significantly increased only in SC (p<0,001). MMP-9 was expressed only in its latent form, being significantly higher in NAC, at 42 hours (p<0,001). This study indicated that only 3% chondroitin sulfate accelerated corneal wound healing. 10% N-acetylcysteine, 1% EDTA and 3% chondroitin sulfate did not protect the corneal epithelial microvilli. In addition, none of the tested agents showed any benefit over MMPs inhibition in alkali burned

Resumo: Estudaram-se os efeitos do sulfato de condroitina 3% (SC), da N-acetilcisteína 10% (NAC), do EDTA 1% (EDTA) e solução salina (GC), sobre a viabilidade do epitélio corneal e a concentração de metaloproteinases (MMP-2 e MMP-9), em córneas de ratos submetidos à ulceração química por NaOH 1N. Compuseram-se quatro grupos de vinte e quatro animais, que foram submetidos à queimadura química corneal com NaOH 1N. Os tratamentos foram realizados a intervalos de 6 horas e as córneas fotografadas, nos mesmos períodos, após tingimento com fluoresceína, até a reepitelização. Doze animais de cada grupo foram submetidos à eutanásia humanitaria, 20 horas após ulcerações. O mesmo procedimento foi repetido às 42 horas para os outros doze animais de cada grupo. As córneas foram processadas para quantificação de microvilosidades do epitelio corneal por microscopia eletrônica de varredura e para quantificação da MMP-2 e -9, por zimografia. O tempo médio de epitelização em horas foi de 28,00±12,82 (SC), 29,00±11,01 (NAC), 35,00±7,01 (EDTA) e de 35,00±7,01 (GC), sem diferença signficativa (p=0,46) entre os grupos. Não se observou diferença quanto ao número de MEC entre os grupos (p>0,05). Às 20 e às 42 horas, a forma latente da MMP-2 foi significativamente mais elevada nos grupos NAC e SC (p<0,001), e às 42 horas observou-se maior concentração em EDTA, relativamente ao GC (p<0,001). Às 42 horas, a concentração da MMP-2, em sua forma ativa, foi significativamente maior, no grupo SC, relativamente aos demais grupos (p<0,001). A MMP-9 só se expressou em sua forma latente, sendo sua concentração significativamente mais elevada, no grupo NAC, às 42 horas (p<0,001). Concluiu-se, que das substâncias testadas, só o sulfato de condroitina acelerou a epitelização corneal, mas nenhuma delas apresentou efeitos protetores às microvilosidades do epitélio corneal ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This study aimed evaluate the effects of topical 3% chondroitin sulfate (SC), 10% N-acetylcysteine (NAC), 1% EDTA (EDTA) and 0,9% NaCl on corneal epithelial viability and the expression of matrix metalloproteinase-2 and -9 (MMP-2 and -9), in alkali burned rat corneas. Ninety eight healthy rats were divided into four groups and animals were submitted to corneal burn with NaOH 1N. All treatments occurred every 6 hours, and the corneas were photographed at the same time points until lesions were fluorescein negative. Twelve animals of each group were euthanized 24 and 42 hours after burn, and corneas were processed for corneal epithelial microvilli quantification (CEM) by scanning electron microscopy and MMP-2 and -9 evaluation by zimography. Images were quantified by Image J. Average corneal wound healing rate was 28,00±12,82 (SC), 29,00±11,01 (NAC), 35,00±7,01 (EDTA) and 35,00±7,01 hours in controls (GC) (p=0,46). CEM count did not change significantly among groups (p>0,05). At 20 and 42 hours, MMP-2 latent form quantity was significantly increased in NAC and SC groups (p<0.001); at 42 hours, MMP-2 latent form was significantly elevated in EDTA, in comparison to GC (p<0,001). At 42 hours, MMP-2 active form was significantly increased only in SC (p<0,001). MMP-9 was expressed only in its latent form, being significantly higher in NAC, at 42 hours (p<0,001). This study indicated that only 3% chondroitin sulfate accelerated corneal wound healing. 10% N-acetylcysteine, 1% EDTA and 3% chondroitin sulfate did not protect the corneal epithelial microvilli. In addition, none of the tested agents showed any benefit over MMPs inhibition in alkali burned / Orientador: José Luiz Laus / Coorientador: Adriana Morales / Banca: Cristiane dos Santos Honsho / Banca: Alexandre Lima de Andrade / Mestre

Prominin-1 is a lipid raft–associated, cholesterol-binding membrane glycoprotein selectively associated with plasma membrane protrusions and extracellular vesicles derived therefrom. Despite its worldwide use for stem cell isolation and its clinical importance in cancer-initiating cells and photoreceptor morphogenesis the function of prominin-1 remains elusive. This prompted me to investigate its role in the architecture and dynamics of microvilli and primary cilia at the apical plasma membrane of Madin-Darby canine kidney (MDCK) cells. Therefore, stably transfected cell lines were established expressing human prominin-1 splice variant 1 or 2. Upon the overexpression of prominin-1 the number of individual microvilli and clusters of them increased significantly. I also noticed alterations in their architecture, i.e. branching microvilli. Fascinatingly, two point mutations (Pro37→Ala and Tyr41→Ser) in the ganglioside GM1-binding motif of prominin-1 increased the number of branched microvilli and generated irregular ones with knob-like structures at their tip. Additionally, the release of prominin-1+ vesicles was impaired. Interestingly, both phenotypes were suppressed by the inhibition of the phosphoinositide 3-kinase (PI3K) or the Arp2/3 complex. Impaired interaction of prominin-1 with the PI3K through the introduction of an additional mutation (Tyr828→Phe) in its PI3K-binding site also reduced the amount of structurally altered microvilli. Thus, the interaction of prominin-1 with the PI3K may drive the conversion of the docking phospholipid phosphatidylinositol(4,5)-bisphosphate into phosphatidylinositol(3,4,5)-trisphosphate resulting in the uncoupling of the microvillar membrane from the underlying actin filaments thereby creating irregular/knob-like microvilli. Simultaneously, the phospholipid conversion might modulate the activity of regulators and/or activators of the Arp2/3 complex leading to the branching of microvilli. The overexpression of human prominin-1 also increased the length of primary cilia. Remarkably, a mutation in the histone deacetylase 6-binding site that mimics acetylation produces shorter cilia in cells expressing human prominin-1.s2. Additionally, it stimulates membrane vesicle release and dome formation. Above these striking observations, I observed branching cilia and cilia with a pearling shape. Collectively, the data suggest that a complex interplay of prominin-1 with its lipid and protein interaction partners regulates the architecture and dynamics of cellular protrusions. Finally, a growing number of studies use canine prominin-1 as an antigenic marker despite the absence of specific antibodies. Studies investigating its expression in dog tissues or cells derived therefrom rely on antibodies directed against its human and murine orthologs. To determine its cross-species immunoreactivity I cloned canine prominin-1 and overexpressed it as a green fluorescent protein fusion protein in MDCK cells. Here, I show that the genomic structure of the canine prom1 gene is similar to that of human and mouse. Canine prominin-1 shows the common characteristics of the prominin-1 family but the primary structure is poorly conserved. Like human and mouse protein, it is targeted to the apical membrane of MDCK cells and specifically enriched in microvilli and primary cilia. Immunocytochemistry, flow cytometry and immunoblotting techniques revealed that none of the applied antibodies against human or mouse prominin-1 recognizes the canine protein.

La détection des stimuli sensoriels est assurée par des cellules réceptrices spécialisées souvent grâce à des protrusions membranaires apicales telles que les microvillosités. La forme finale des extensions apicales microvilliées conditionne de nombreuses propriétés de la transduction sensorielle mais leur formation reste méconnue. Quels sont les facteurs moléculaires responsables de l’initiation et de l’élongation des filaments d’actine chez les cellules sensorielles microvilliées (CSMs) ? Peut-on décrire des éléments clés de la morphogenèse en commun ? Quel est le rôle structurel des microvillosités dans la fonction sensorielle ?J’ai étudié deux types sensoriels microvilliés : les neurones contactant le liquide cérébrospinal (NcLCS) et les cellules sensorielles des neuromastes (CSn). Mon projet visait à investiguer les mécanismes moléculaires sous-jacents à la morphogenèse des CSMs par l’étude des NcLCS. J’ai décrit les étapes critiques menant à la formation de l’extension apicale des NcLCS auxquelles j’ai pu associer des candidats potentiels grâce l’analyse transcriptomique des NcLCS. J’ai démontré le rôle critique de l’interaction entre Espin et Myo3b dans l’élongation de l’extension apicale des NcLCS et j’ai établi un lien direct entre structure et fonction en montrant que le raccourcissement de l’extension apicale aboutissait à la réduction de la réponse sensorielle.Mon travail a permis d’apporter des éléments de réponse quant à la formation de l’organe sensoriel des NcLCS. L’analyse transcriptomique des CSn a par ailleurs révélé des facteurs de morphogenèse communs avec les NcLCS, suggérant que toutes les CSMs partagent des propriétés de différenciation conservées. / Sensory systems use specialized receptor cells, many of which detect sensory cues through specialized apical membrane protrusions, such as microvilli. The final shape of the microvilliated apical extension requires specific molecular machinery and determines many of the properties of sensory transduction. The establishment of this structure remains however elusive. What molecular factors orchestrate the initiation and elongation of actin filaments in microvilliated sensory cells (MSCs)? Can we find key elements of morphogenesis common to MSCs? What is the precise role of microvilli structure in sensory function? I investigated two sensory cell types harboring microvilli: spinal cerebrospinal fluid-contacting neurons (CSF-cNs) and neuromast hair cells (nHCs). The primary goal was to unravel the molecular mechanisms underlying morphogenesis of MSCs by focusing on CSF-cNs. I was able to describe critical steps leading to the development of CSF-cN apical extension. My participation to the transcriptome analysis of CSF-cNs revealed candidate molecular factors associated with each of these steps. I demonstrated the importance of the interaction between Espin and Myo3b to ensure the proper lengthening of CSF-cN apical extension. In this system, I established a direct link between morphology and function by showing that shorter apical extensions lead to reduced sensory response. Altogether, my work shed light on the formation of CSF-cN sensory organelle and its functional role. In parallel, the establishment of the nHC transcriptome dataset revealed similar morphogenetic factors with CSF-cNs, supporting the idea that all MSCs share conserved features for their differentiation.

Prominin-1 is a lipid raft–associated, cholesterol-binding membrane glycoprotein selectively associated with plasma membrane protrusions and extracellular vesicles derived therefrom. Despite its worldwide use for stem cell isolation and its clinical importance in cancer-initiating cells and photoreceptor morphogenesis the function of prominin-1 remains elusive. This prompted me to investigate its role in the architecture and dynamics of microvilli and primary cilia at the apical plasma membrane of Madin-Darby canine kidney (MDCK) cells. Therefore, stably transfected cell lines were established expressing human prominin-1 splice variant 1 or 2. Upon the overexpression of prominin-1 the number of individual microvilli and clusters of them increased significantly. I also noticed alterations in their architecture, i.e. branching microvilli. Fascinatingly, two point mutations (Pro37→Ala and Tyr41→Ser) in the ganglioside GM1-binding motif of prominin-1 increased the number of branched microvilli and generated irregular ones with knob-like structures at their tip. Additionally, the release of prominin-1+ vesicles was impaired. Interestingly, both phenotypes were suppressed by the inhibition of the phosphoinositide 3-kinase (PI3K) or the Arp2/3 complex. Impaired interaction of prominin-1 with the PI3K through the introduction of an additional mutation (Tyr828→Phe) in its PI3K-binding site also reduced the amount of structurally altered microvilli. Thus, the interaction of prominin-1 with the PI3K may drive the conversion of the docking phospholipid phosphatidylinositol(4,5)-bisphosphate into phosphatidylinositol(3,4,5)-trisphosphate resulting in the uncoupling of the microvillar membrane from the underlying actin filaments thereby creating irregular/knob-like microvilli. Simultaneously, the phospholipid conversion might modulate the activity of regulators and/or activators of the Arp2/3 complex leading to the branching of microvilli. The overexpression of human prominin-1 also increased the length of primary cilia. Remarkably, a mutation in the histone deacetylase 6-binding site that mimics acetylation produces shorter cilia in cells expressing human prominin-1.s2. Additionally, it stimulates membrane vesicle release and dome formation. Above these striking observations, I observed branching cilia and cilia with a pearling shape. Collectively, the data suggest that a complex interplay of prominin-1 with its lipid and protein interaction partners regulates the architecture and dynamics of cellular protrusions. Finally, a growing number of studies use canine prominin-1 as an antigenic marker despite the absence of specific antibodies. Studies investigating its expression in dog tissues or cells derived therefrom rely on antibodies directed against its human and murine orthologs. To determine its cross-species immunoreactivity I cloned canine prominin-1 and overexpressed it as a green fluorescent protein fusion protein in MDCK cells. Here, I show that the genomic structure of the canine prom1 gene is similar to that of human and mouse. Canine prominin-1 shows the common characteristics of the prominin-1 family but the primary structure is poorly conserved. Like human and mouse protein, it is targeted to the apical membrane of MDCK cells and specifically enriched in microvilli and primary cilia. Immunocytochemistry, flow cytometry and immunoblotting techniques revealed that none of the applied antibodies against human or mouse prominin-1 recognizes the canine protein.

Enterohemorrhagic E. coli (EHEC) is a major cause of food borne diarrheal illness worldwide. While disease symptoms are usually self-resolving and limited to severe gastroenteritis with bloody diarrhea, EHEC infection can lead to a life threatening complication known as Hemolytic Uremic Syndrome (HUS), which strikes children disproportionately and is the leading cause of kidney failure in children. Upon infection of gut epithelia, EHEC produces characteristic lesions called actin pedestals. These striking formations involve dramatic rearrangement of host cytoskeletal proteins. EHEC hijacks mammalian signaling pathways to cause destruction of microvilli and rebuilds the actin cytoskeleton underneath sites of bacterial attachment. Here, we present a brief study on a host factor, Calpain, involved in microvilli effacement, and an in depth investigation on a bacterial factor, EspFU, required for actin pedestal formation in intestinal cell models. Calpain is activated by both EHEC and the related pathogen, enteropathogenic E. coli (EPEC), during infection and facilitates microvilli disassembly by cleavage of a key membrane-cytoskeleton anchoring substrate, Ezrin. Actin pedestal formation is facilitated by the injection of two bacterial effectors, Tir and EspFU, into host cells, which work in concert to manipulate the host actin nucleators N-WASP and Arp2/3. EspFU hijacks key host signaling proteins N-WASP and IRTKS by mimetic displacement and has evolved to outcompete mammalian host ligands. Multiple repeats of key functional domains of EspFU are essential for actin pedestal activity through proper localization and competition against the an abundant host factor Eps8 for binding to IRTKS.

Os estudos da função intestinal foram particularmente estimulados após a conscientização de que o tubo digestivo é uma enorme interface relativamente pouco protegida entre o inseto e o meio ambiente e pode ser usado como alvo para controle de pragas. Neste contexto, nosso trabalho envolve a purificação e caracterização de uma &#945;-manosidase solúvel e a detecção de uma &#945;-manosidase de membrana. As &#945;-manosidases pertencem a uma família de exoglicosidases as quais hidrolisam resíduos de &#945;-D-manosil a partir de terminais não redutores de oligossacarídeos. Estas enzimas são implicadas no catabolismo de carboidratos e na via de N-glicosilação protéica em insetos, mas pouco se sabe sobre a bioquímica destas glicosidases. O Tenebrio molitor é um Coleoptera bastante estudado pelo nosso laboratório devido a sua relevância como praga agrícola e o seu posicionamento em um ponto estratégico da árvore filogenética de insetos. O estudo de distribuição desta enzima mostrou que a &#945;-manosidase encontra-se, principalmente, como uma enzima solúvel no conteúdo anterior e médio do intestino médio, mas também existe uma atividade significante na fração de membrana. Para confirmar a existência desta enzima de membrana, microvilosidades foram purificadas por precipitação diferencial com cálcio. A enzima aminopeptidase foi utilizada como marcadora, uma vez que sabe-se que esta enzima é uma típica de membrana microvilar. Como a &#945;-manosidase solúvel é majoritária demos início a sua purificação e posterior caracterização. A sua purificação foi realizada utilizando uma combinação de quatro passos de cromatografia: Uma de troca iônica em Hitrap Q XL (Amersham/Bioscience), duas filtrações em gel, uma em Superdex 75 e outra em Superdex 200 (Amersham/Bioscience) usando o sistema AKTA, e o último passo é uma hidrofóbica em Phenyl Superose. Nós observamos a presença de dois picos de atividade nomeados de Man 1 e Man 2, sugerindo a existência de duas &#945;- manosidases solúveis, que se diferem quanto a hidrofobicidade. O pH ótimo das &#945;-manosidases é de 5,6 e sua massa molecular, determinada por cromatografia de 8 filtração em gel, é de 123 kDa, e no SDS-PAGE observamos uma única banda de 70 KDa, indicando a existência de duas subunidades. Em um gel nativo revelado com o substrato fluorescente (metilumbelliferil-&#945;-D-manopiranosídeo) nota-se somente uma banda de atividade. A Man 2 possui pI de 3,38. &#945;-manosidases de T. molitor seguem a cinética de Michaelis-Menten com Km para o substrato p-nitrofenil-&#945;-D-manopiranosídeo de 0,84 mM para Man 1 e 0,62 mM para Man 2. Também foram feitos ensaios de inibição com dois inibidores que sabidamente inibem carboidrases, um é o deoximanojirimicina e o outro é a swainsonina. O Ki encontrado para o primeiro inibidor foi de 0,12 mM para Man 1 e 0,15 mM para Man 2 e o Ki para o segundo inibidor foi de 67,8 nM para Man 1 e 63 nM para Man 2, sendo ambos inibidores competitivos. O fato destas enzimas serem inibidas apenas por Swainsonina em concentrações razoáveis, permite a sua classificação como tipo II. Isso sugere que elas são derivadas da forma lisossômica, embora apresente pH ótimo alterado. / Studies of intestinal function were prompted after noticing that the gut is a huge and relatively unprotected interface between the insect and the environment and can thus be used as a target for pest control. In this context, our work involves the purification and characterization of an soluble alpha-mannosidase and detection of a membrane &#945;-mannosidase. &#945;-Mannosidases are a family of exoglycosidases which hydrolyse &#945;-D-mannosyl residues from terminal non-reducing end of oligossacharides. These enzymes are implicated in the catabolism of carbohydrates and N-linked protein glycosylations in insects, but little is known on this biochemistry. T.molitor is a Coleoptera studied in our laboratory because of its relevance as agricultural pest and its position at a strategic point in the phylogenetic tree of insects. &#945;-Mannosidase is more active in the anterior and middle midgut content of T.molitor larvae, although there is a significant activity in the membrane fraction. To confirm the existence of this membrane enzyme, microvilli were purified by differential precipitation with calcium. Aminopeptidase was used as a marker, since it is known that it is a typical microvilar membrane enzyme. Most &#945;-mannosidase activity is soluble. This led us to purify this enzyme for further characterization. The purification of T. molitor &#945;-mannosidase was attained by using a combination of four chromatographic steps: an anion-exchange chromatography in Hitrap Q XL (Amersham/Bioscience), two gel filtration chromatographies, one in Superdex 200 and another in Superdex 75 (Amersham/Bioscience) using an AKTA system, and the last step is a Hydrophobic cromatography in Phenyl Superose. Two peaks of activity were resolved: Man 1 and Man 2, suggesting the existence of two soluble &#945;-mannosidases, differing only in hydrophobicity. The optimum pH of the &#945;- mannosidases is 5.6 and the molecular mass is 123 KDa determined by gel filtration and 70 KDa in the case of SDS PAGE. This suggests that the holoenzyme has two subunits. In a native gel revealed with the fluorescent substrate (methylumbelliferyl-&#945;-D-mannopyranoside) only one band of activity is seen. Man 2 has pI 3.38. T. molitor &#945;-mannosidases followed Michaelis-Menten kinetics with a Km value of 0.84 mM for Man 1 and 0.62 mM for Man 2 using p-nitrophenyl-&#945;-D-mannopyranoside as substrate. Inhibition tests were made with typical inhibitors of &#945;-mannosidases: one is the 1-deoxymannojirimycin and the other is the Swainsonine. The Ki for the first was of 0.12 mM for Man 1 and 0.15 mM for Man 2 and for the second was 67.8 nM for Man 1 and 63 nM for Man 2. Both were competitive inhibitors. The fact that the enzymes are inhibited only by swainsonine in reasonable concentrations, allows us to classify them as type II. This suggests that they are derived from the lysosomal form, although they have an altered optimum pH.