Recycling embosoms (REs) are transient intermediates of endosomal network, constantly generated from early/sorting endosomes (EEs/SEs). Conventionally, these organelles function in recycling of many growth/nutrient/signalling receptors from SEs to the cell surface and maintain the cellular homeostasis in all cell types. Recent studies have shown that REs slightly diverted their function in specialized cells such as melanocytes for the delivery of melanogenic cargo to a set of lysosome-related organelles (LROs) called melanosomes. However, it is unknown how melanocytes modulate the trafficking routes of REs towards the biogenesis of melanosomes. Any alterations in this process result in occulocutaneous albinism, commonly observed in autosomal recessive disorder, Hermansky-Pudlak Syndrome (HPS). HPS is caused by mutations in nine genes in human and fifteen genes in mouse and the protein products of these genes were grouped in multiple endosomal protein complexes; BLOC (Biogenesis of Lysosome-related Organelles Complex)-1, -2, -3, AP (Adaptor Protein)-3 and HOPS (homotypic fusion and protein sorting). Studies from our laboratory and others have shown that REs deliver the melanin-synthesizing enzymes to melanosome in BLOC-1 and BLOC-2 dependent manner. On the other side, studies in fibroblasts have shown that the adaptor AP-1 and microtubule-dependent motor, KIF13A also regulates the formation of REs. In these studies, it was proposed that AP-1 binds to the cargo tails and interacts with motor KIF13A to generate the RE tubules, where BLOC-1 initiates the biogenesis. Nevertheless, the mechanism behind the biogenesis of REs and how these molecules synergistically control these processes is largely unknown. Additionally, the role of BLOC-2 in REs biogenesis never been implicated. Here we have attempted to study the mechanism of RE biogenesis and their role in pigment granule formation using HeLa and mouse melanocytes as model systems. In general, Rab GTPases (Rabs) regulate the several process of membrane trafficking including cargo sorting, membrane domain organization, tethering and fusion. We hypothesized that the biogenesis of RE is also regulated by one of the endosome localized Rab GTPases. Our RNAi screening against Rabs involved in regulating the RE length/number showed Rab22A as a potential candidate. Thus, we aim to study the role of Rab22A in RE biogenesis and its regulation in melanocyte pigmentation. The current study entitled as “Understanding the role of Rab22A in recycling endosome biogenesis and melanocyte pigmentation” is divided into five chapters. Chapter-I outlines the review of literature on cell biology of intracellular organelles such as endocytic network and melanosomes. Chapter-II details the experimental procedures used in the study. Chapter-III to Chapter-V describes the results and discussion. Chapter-III: Identification of endosomal Rab GTPases required for the dynamics of recycling endosomes Endosomal Rabs are known to regulate various functions such as vesicle biogenesis, transport, tethering and fusion, but their role in generation of tubulo-vesicular carriers of endocytic system, REs is unknown. It has been shown that REs possibly derived from EEs/SEs and characterized by the association/localization of multiple proteins such as transferrin receptor (TfR), SNARE STX13, Rab11 and motor KIF13A. In this study, we have used YFP-KIF13A as a marker to label the REs. YFP-KIF13A in HeLa cells localized to long tubular structures throughout the cell and also to the clusters of peripheral endosomes. To identify the endosomal Rabs that regulate the RE dynamics (both length and number), we have transfected the HeLa cells with shRNA against endosomal Rabs such as Rab4A, Rab5A, Rab5B, Rab5C, Rab7A, Rab9A, Rab11A, Rab14A and Rab22A. Post transfection and shRNA selection, cells were transfected with YFP-KIF13A, analyzed and quantified the RE dynamics using ImageJ. Here, we have measured two parameters for the identification of Rab/s that potentially regulates the REs biogenesis: first, average number of tubules per cell and second, average length of tubules per cell. These studies identified Rab22A as a potential candidate, depletion of this Rab affects both number and average length of KIF13A-positive tubules. As described above, REs deliver several melanocyte specific cargoes to melanosomes in melanocytes. However, the function of Rab22A in controlling these transport steps to melanosome/its biogenesis or pigmentation has not been addressed. Thus, we have studied the mechanism of Rab22A in RE biogenesis and its role in pigmentation in the following sections. Chapter-IV: Characterization of Rab22A function in regulating the recycling endosomes Initially, we tested whether Rab22A localizes to the REs. Our co-expression studies show that Rab22A localizes to KIF13A- or STX13-positive RE compartments in HeLa or melanocytes, respectively. In general, Rab GTPases mediate their function through cycling between GTP (membrane bound) and GDP (cytosol) bound state. These states can be achieved by point mutation of active site residues in the protein. We have generated Rab22A constitutive active mutant (Rab22AQ64L, defective in GTP hydrolysis) and dominant negative mutant (Rab22AS19N, defective in GTP binding) to understand the role of Rab22A in regulating REs. Interestingly, overexpression of Rab22AQ64L mutant in HeLa cells increases the average number of KIF13A-positive REs relative to the wild-type Rab22A (Rab22AWT). As predicted, overexpression of Rab22AS19N mutant reduces the number as well as length of RE tubules relative to the control HeLa cells. Consistent to these studies, Rab22A-knockdown did not affect the endogenous KIF13A protein levels or its recruitment to endosomes, however recycling of TfR (measured through Tf-Alexa 594) was significantly affected in these cells. These studies suggest that Rab22A possibly regulates the formation or function of REs. Likewise, overexpression of Rab22AQ64L and Rab22AS19N mutants in melanocytes resulted in reduction of total melanin content in the cells. To confirm these results, we have performed immunofluorescence microscopy (IFM) analysis, which showed Rab22AQ64L localized to the enlarged vacuolar structures, positive for melanosomal cargo TYRP1 (tyrosinase-related protein 1), whereas Rab22AS19N localized to the cytosol. Further, Rab22A depletion in melanocytes causes the hypopigmentation in the cells concurrently reduces the stability of TYRP1 but not other melanocyte specific proteins, indicating a role for Rab22A in regulating TYRP1 transport to melanosomes. Altogether, our studies suggests that Rab22A regulates the TfR recycling in HeLa cells and TYRP1 transport in melanocytes by controlling the RE dynamics. Chapter-V: Molecular mechanism of recycling endosome biogenesis: a role for Rab22A Rabs perform their function by recruiting specific effector/s to the membrane upon Rab activation. It is unknown, how Rab22A regulates REs through its effectors. We hypothesize that Rab22A may regulate the recruitment and function of BLOC-1 and BLOC-2 complexes during RE formation. To validate these hypothesis, we carried out the knockdown of individual BLOC-1 and -2 subunits (destabilize the entire complex) separately in HeLa and studied the dynamics of RE through YFP-KIF13A expression. As expected, the length and number of KIF13A-postive tubules were significantly reduced in both BLOC-1- and BLOC-2-deficient HeLa cells and was phenocopying the Rab22A knockdown cells. Moreover, subcellular fractionation in HeLa, co-fractionated Rab22A with BLOC-1 (Muted) or BLOC-2 (HPS6) subunits along with KIF13A. Additionally, endogenous subunit levels of BLOC-1 and BLOC-2 were moderately reduced in Rab22A knockdown HeLa cells. Consistent to these results, recycling kinetics of Transferrin (Tf) was altered in Rab22A depleted cells as similar to BLOC-1- or BLOC-2-deficient cells as reported earlier. Likewise, Rab22A knockdown in melanocytes affected STX13-positive tubules and also the stability of endogenous BLOC-1 subunit, Pallidin, suggesting that Rab22A possibly works with BLOC-1 and BLOC-2 independent of cell types. To understand the regulation among these molecules, we overexpressed Rab22A in BLOC-1-deficient cells and analyzed the cells for BLOC-1-deficient rescue phenotypes such as pigmentation and cargo localization. However, Rab22A could not compensate the BLOC-1 function, suggesting that Rab22A possibly functions upstream of BLOC-1. Our subcellular and membrane associated fractionation studies of homogenates depleted with Rab22A, BLOC-1 and BLOC-2 showed that subunit levels of BLOC-1 and BLOC-2 in the membrane pool were significantly reduced upon Rab22A depletion compared to control cells. However, membrane association of Rab22A in BLOC-1 deficient cells was not affected. Further, our biochemical interaction studies showed that Rab22A interacts physically with BLOC-1 and BLOC-2 subunits as well as with KIF13A. Thus, these studies indicate that Rab22A possibly recruits and interacts with BLOC-1 and BLOC-2 for the generation of REs. We have summarized the study by proposing a model wherein Rab22A localizes to the limiting membrane of endosomes that are positive for KIF13A and then recruits and associates with BLOC-1 and BLOC-2 complexes which subsequently pulled by KIF13A for the generation of RE tubules.

No description available.

<p>It is well-established that the organization of nuclear components influences gene expression processes, yet little is known about the mechanisms that contribute to the spatial co-ordination of nuclear activities. The salivary gland cells of <i>Chironomus tentans</i> provide a suitable model system for studying gene expression<i> in situ</i>, as they allow for direct visualization of the synthesis, processing and export of a specific protein-coding transcript, the Balbiani ring (BR) pre-mRNA, in a nuclear environment in which chromatin and non-chromatin structures can easily be distinguished. The RNAbinding protein Hrp65 has been identified in this model system as a protein associated with non-chromatin nucleoplasmic fibers, referred to as connecting fibers (CFs). The CFs associate with BR RNP particles in the nucleoplasm, suggesting that Hrp65 is involved in mRNA biogenesis at the post-transcriptional level. However, the function of Hrp65 is not known, nor is the function or the composition of CFs. In the work described in this thesis, we have identified by yeast two-hybrid screening and characterized different proteins that bind to Hrp65. These proteins include a novel hnRNP protein in <i>C. tentans</i> named Hrp59, various isoforms of Hrp65, the splicing- and mRNA export factor HEL/UAP56, and a RING-domain protein of unknown function. Immuno-electron microscopy experiments showed that Hrp59 and HEL are present in CFs, and in larger structures in the nucleoplasm of <i>C. tentans</i> salivary gland cells.</p><p>Hrp59 is a <i>C. tentans</i> homologue of human hnRNP M, and it associates cotranscriptionally with a subset of pre-mRNAs, including its own transcript, in a manner that does not depend quantitatively on the amount of synthesized RNA. Hrp59 accompanies the BR pre-mRNA from the gene to the nuclear envelope, and is released from the BR mRNA at the nuclear pore complex. We have identified the preferred RNA targets of Hrp59 in <i>Drosophila</i> cells, and we have shown that Hrp59 binds preferentially to exonic splicing enhancer sequences.</p><p>Hrp65 self-associates through an evolutionarily conserved domain that can also mediate heterodimerization of Hrp65 homologues. Different isoforms of Hrp65 interact with each other in all possible combinations, and Hrp65 can oligomerize into complexes of at least six molecules. The interaction between different Hrp65 isoforms is crucial for their intracellular localization, and we have discovered a mechanism by which Hrp65-2 is imported into the nucleus through binding to Hrp65-1.</p><p>Hrp65 binds to HEL/UAP56 in <i>C. tentans</i> cells. We have analyzed the distribution of the two proteins on polytene chromosomes and in the nucleoplasm of salivary gland cells, and our results suggest that Hrp65 and HEL become associated during posttranscriptional gene expression events. HEL binds to the BR pre-mRNP cotranscriptionally, and incorporation of HEL into the pre-mRNP does not depend on the location of introns along the BR pre-mRNA. HEL accompanies the BR mRNP to the nuclear pore and is released from the BR mRNP during translocation into the cytoplasm.</p>

Maintaining energy organismal homeostasis under changing physiological and environmental conditions is vital, and requires constant adjustments of the energy metabolism. Central to meeting energy demands is the regulation of mitochondrial oxidative capacity. When demands increase, animals can increase mitochondrial content/enzymes, known as mitochondrial biogenesis. Central to mammalian mitochondrial biogenesis is the transcriptional master regulator PPARγ (peroxisome proliferator-activated receptor γ) coactivator-1α (PGC-1α), and the network of DNA-binding proteins it coactivates (e.g. nuclear respiratory factor 1 and 2 [NRF-1, NRF-2], estrogen-related receptor α [ERRα], thyroid receptor α [TRα-1], retinoid X receptor α [RXRα]). However, the mechanisms by which mitochondrial content in lower vertebrates such as fish is controlled are less studied. In my study I investigate underlying mechanisms of the phenomenon that many fish species alter mitochondrial enzyme activities, such as cytochrome c oxidase (COX) in response to low temperatures. In particular, I investigated (i) if the phenomenon of mitochondrial biogenesis during cold-acclimation is related to fish phylogeny, (ii) what role PGC-1α and other transcription factors play in mitochondrial biogenesis in fish, and (iii) if mRNA decay rates are important in the transcriptional control of a multimeric protein like COX. This study shows that mitochondrial biogenesis does not follow a phylogenetic pattern: while distantly related species displayed the same response to low temperatures, closely related species showed opposite responses. In species exhibiting mitochondrial biogenesis, little evidence was found for PGC-1α as a master regulator, whereas NRF-1 is supported to be an important regulator in mitochondrial biogenesis in fish. Further, there was little support for other transcription factors (NRF-2, ERRα, TRα-1, RXRα) to be part of the regulatory network. Lastly, results on the post-transcriptional control mechanism of mRNA decay indicate that this mechanism is important in the regulation of COX under mitochondrial biogenesis: it accounts for up to 30% of the change in subunit transcript levels. In summary, there is no simple temperature-dependent mitochondrial response ubiquitous in fish. Further, the pathways controlling mitochondrial content in fish differ from mammals in the important master regulator PGC-1α, however, NRF-1 is important in regulating cold-induced mitochondrial biogenesis in fish. Lastly, COX subunit mRNA decay rates seem to have a part in controlling COX amounts during mitochondrial biogenesis. / Thesis (Ph.D, Biology) -- Queen's University, 2013-10-21 09:53:59.46

<p>The six-layered neuron structure in the cerebral cortex is the foundation for human mental abilities. In the developing cerebral cortex, neural stem cells undergo proliferation and differentiate into intermediate progenitors and neurons, a process known as embryonic neurogenesis. Disrupted embryonic neurogenesis is the root cause of a wide range of neurodevelopmental disorders, including microcephaly and intellectual disabilities. Multiple layers of regulatory networks have been identified and extensively studied over the past decades to understand this complex but extremely crucial process of brain development. In recent years, post-transcriptional RNA regulation through RNA binding proteins has emerged as a critical regulatory nexus in embryonic neurogenesis. The exon junction complex (EJC) is a highly conserved RNA binding complex composed of four core proteins, Magoh, Rbm8a, Eif4a3, and Casc3. The EJC plays a major role in regulating RNA splicing, nuclear export, subcellular localization, translation, and nonsense mediated RNA decay. Human genetic studies have associated individual EJC components with various developmental disorders. We showed previously that haploinsufficiency of Magoh causes microcephaly and disrupted neural stem cell differentiation in mouse. However, it is unclear if other EJC core components are also required for embryonic neurogenesis. More importantly, the molecular mechanism through which the EJC regulates embryonic neurogenesis remains largely unknown. Here, we demonstrated with genetically modified mouse models that both Rbm8a and Eif4a3 are required for proper embryonic neurogenesis and the formation of a normal brain. Using transcriptome and proteomic analysis, we showed that the EJC posttranscriptionally regulates genes involved in the p53 pathway, splicing and translation regulation, as well as ribosomal biogenesis. This is the first in vivo evidence suggesting that the etiology of EJC associated neurodevelopmental diseases can be ribosomopathies. We also showed that, different from other EJC core components, depletion of Casc3 only led to mild neurogenesis defects in the mouse model. However, our data suggested that Casc3 is required for embryo viability, development progression, and is potentially a regulator of cardiac development. Together, data presented in this thesis suggests that the EJC is crucial for embryonic neurogenesis and that the EJC and its peripheral factors may regulate development in a tissue-specific manner.</p> / Dissertation

Messenger RNA degradation is crucial for the regulation of eukaryotic gene expression. It not only modulates the basal mRNA levels but also functions as a quality control system, thereby controlling the availability of mRNA for protein synthesis. In Saccharomyces cerevisiae, the first and the rate-limiting step in the process of mRNA degradation is the shortening of the poly(A) tail by deadenylation complex. After the poly(A) tail shortens, mRNA can be degraded either through the major 5' to 3' decapping dependent or the 3' to 5' exosome-mediated degradation pathway. In this thesis, we show some of the means by which mRNA decay factors can modulate gene expression. First, Pat1 is a major cytoplasmic mRNA decay factor that can enter the nucleus and nucleo-cytoplasmically shuttle.  Recent evidence suggested several possible nuclear roles for Pat1. We analyzed them and showed that Pat1 might not function in pre-mRNA decay or pre-mRNA splicing, but it is required for normal rRNA processing and transcriptional elongation. We show that the mRNA levels of the genes related to ribosome biogenesis are dysregulated in the strain lacking Pat1, a possible cause of the defective pre-rRNA processing. In conclusion, we theorize that Pat1 might regulate gene expression both at the level of transcription and mRNA decay. Second, Edc3 and Lsm4 are mRNA decapping activators and mRNA decay factors that function in the assembly of RNA granules termed P bodies. Mutations in mRNA degradation factors stabilize mRNA genome-wide or stabilize individual mRNAs. We demonstrated that paradoxically, deletion of Edc3 together with the glutamine/asparagine-rich domain of Lsm4 led to a decrease in mRNA stability. We believe that the decapping activator Edc3 and the glutamine/asparagine-rich domain of Lsm4 functions together, to modify mRNA decay pathway by altering cellular mRNA decay protein abundance or changing the mRNP composition or by regulating P bodies, to enhance mRNA stability. Finally, mRNA decay was recently suggested to occur on translating ribosomes or within P bodies. We showed that mRNA degradation factors associate with large structures in sucrose density gradients and this association is resistant to salt and sensitive to detergent. In flotation assay, mRNA decay factors had buoyancy consistent with membrane association, and this association is independent of stress, translation, P body formation or RNA. We believe that such localization of mRNA degradation to membranes may have important implications in gene expression. In conclusion, this thesis adds to the increasing evidence of the importance of the mRNA degradation factors in the gene expression.

Mitochondrion is believed to be an ubiquitous organelle which occurred about 1,5 billion years ago by a single endosymbiotic event. Mitochondria is mostly dependent on the protein import from cytosol thus the establishment of protein import machinery was essential for seizing the new endosymbiont. Possibilities of studying the evolution of protein import machineries are quite limited given that no "free living" mitochondria or amitochondriate organisms are known nowadays. One alternative is to study mitochondrial secondary reductive evolution of anaerobic parasitic protists. Giardia intestinalis is flagellated protozoan living in microaerofilic environment of the small intestine. It containes one of the most reduced mitochondrion (mitosome) described so far. Hence it serves as a great model for studying mitochondrial evolution. Although it is well understood that all mitosomal proteins are transported from cytosol, many aspects of protein import pathway remain elusive. While the main channel Tom40 is present in the outer membrane, two other main translocases (Sam50 which is required for betta-barrel assembly in the outer membrane and Tim17/22/23 which is essential for protein translocation through the inner membrane) have not been identified so far. Protein translocation through Tim17/22/23 channel...

Les molybdoenzymes sont des métalloprotéines retrouvées chez tous les êtres vivants, des procaryotes à l’Homme. Chez les organismes procaryotes, leur repliement et leur assemblage est un processus complexe nécessitant l’intervention de protéines chaperons spécifiques qui coordonnent l’insertion des centres métalliques au repliement et à l’assemblage des différentes sous-unités. Au cours de ma thèse, je me suis intéressé au rôle du gène fdhD indispensable à l’activité des formiate déshydrogénases chez Escherichia coli et plus précisément sur son importance vis-à-vis de l’une d’entre elles, FdhF, une métalloprotéine à fer, molybdène et sélénium. FdhD interagit d’une part, avec sa cible FdhF et d’autre part, avec IscS, cystéine désulfurase majeure et impliquée notamment dans la biosynthèse des centres [Fe-S]. L’analyse de la séquence de FdhD met en évidence la présence d’un motif C121GXC124 conservé dont la substitution des résidus cystéine en alanine abolit la fonction de FdhD. En interagissant avec IscS, FdhD stimule son activité cystéine désulfurase et récupère le soufre généré en le fixant sous la forme de persulfures. La substitution des résidus cystéine a pour conséquence de réduire l’efficacité de transfert de soufre entre IscS et les variants de FdhD. La perte totale de l’activité FdhF enregistrée, en absence de FdhD, n’est pas due à une instabilité ou à un défaut d’insertion des centres métalliques mais est causée par une perte de sulfuration de l’enzyme. Sur la base de mes résultats, nous proposons que FdhD soit une soufre transférase entre IscS et FdhF. La sulfuration de FdhF par FdhD est essentielle à son activité enzymatique. Ce modèle est en accord avec les données cristallographiques indiquant la présence d’un atome de soufre au niveau de la sphère de coordination du Mo dans le site actif des formiate deshydrogénases et permet d’aller plus loin en reliant la présence du soufre à un état actif de l’enzyme et en identifiant les acteurs du processus. / Molybdoenzymes are ubiquitous metalloproteins found from prokaryotes to human. In prokaryotes, their folding and assembly is an intricate process assisted by dedicated chaperones coordinating metal centers insertion to folding and assembly of several subunits.During my PhD, I have investigated the role of the fdhD gene absolutely required for formate dehydrogenase activities in Escherichia coli and more precisely on one of them, FdhF, an iron-molybdenum-selenium metalloprotein. FdhD interacts with its target, FdhF and with IscS, a major cysteine desulfurase involved for instance in Fe-S cluster biogenesis. Sequence analysis of FdhD reveals the existence of a conserved C121GXC124 motif. Substitution of any of the two cysteine residues abolished FdhD function. Through IscS interaction, FdhD stimulates cysteine desulfurase activity and binds the sulfide generated by IscS in the forms of persulfides. Substitution of any of the conserved cysteine residues of FdhD reduces the sulfur transfer efficiency from IscS. Loss of FdhF activity in absence of fdhD is not due to intrinsic instability of loss of metal centers but rather due to lack of enzyme sulfuration. Based on my results, we postulate that FdhD functions as a sulfur transferase between IscS and FdhF, an essential step for enzyme activity. Our model is in complete agreement with crystallographic data showing the presence of a sulfur atom at the coordination sphere of the Mo atom at the active site of formate dehydrogenases and furthermore allows reconciling the presence of sulfur at the active site with enzymatic activity and identifying the players in this process.

The Hap2/3/4/5 complex is a heme-activated, CCAATT binding, global transcriptional activator of genes involved in respiration and mitochondrial biogenesis in the yeast species Saccharomyces cerevisiae. Hap4 is the regulatory subunit of the complex and its levelsdetermine the activity of the complex. Hap4 is known to play a signaling role in response toenvironmental conditions; however, little is known about the regulation of Hap4 levels or how it responses to a cell’s functional state. The activity of the Hap2-5 complex is known to be reduced in respiratory-deficient cells. In Liu Lab, it has previously been found that a link between Hap4 stability, mediated through 26S proteasome-dependent degradation, and dependence on mitochondrial functional state plays a regulatory role on downstream targets of the Hap complex. However, the mechanism behind this regulation is still largely unknown. In normally functioning yeast cells, Hap4 is a highly unstable protein with a half-life of ~10 min. We have observed that loss of mitochondrial DNA in respiratory deficient rho 0 cells has a role in the further destabilization of Hap4 to a half-life of ~4 min through the ubiquitin-proteasome pathway. Through the screening of a collection of mutants defective in E2 ubiquitin-conjugating enzymes, we show that Hap4 is greatly stabilized in ubc1Δubc4Δ double mutant cells. We also show that Hap4 stabilization in the ubc1Δubc4Δ mutant leads to increased activity of the Hap2-5 complex, indicating that mitochondrial biogenesis in yeast is regulated by the functional state of mitochondria through ubiquitin/proteasome-dependent degradation of Hap4. Furthermore, studies on Hap4 mutants involving two highly conserved cysteine residues led to a proposed mechanism behind the regulation of Ubc4 activity towards Hap4 in response to changes in the cellular redox state.

O tema desta pesquisa é a influência da atividade de minhocas no solo de uma vertente do Planalto Atlântico Paulista. O local estudado está cercado por áreas de preservação ambiental, possui florestas primárias em bom estado de conservação e apresenta clima quente com precipitações acima dos 2.000 mm por ano. Foi feito um levantamento das comunidades de anelídeos a partir de três diferentes técnicas de extração. Os organismos coletados foram identificados em nível de espécie e sua distribuição foi analisada ao longo da topografia. Demonstrou-se uma variação das populações de minhocas nos três setores da vertente, com maiores densidades no sopé e menores no topo. Verificou-se que há uma intensa atividade desses organismos no solo e que eles não se distribuem igualmente no perfil vertical, concentrando-se em algumas camadas, às vezes superficiais às vezes subsuperficiais, de acordo com o tipo de solo. Observou-se também a presença de espécies exóticas nas áreas antrópicas. Foi constatado que a atividade desses organismos modifica a morfologia (bioagregação) e também os atributos físicos (macroporosidade; bioporos) e químicos do solo (teores de matéria orgânica e dos nutrientes P, K+, Ca2+ e Mg2+; soma de bases; capacidade de troca catiônica), influenciando diversos processos pedológicos. Com seus comportamentos ecológicos (alimentar e construtor), as minhocas criam galerias, canais e produzem dejeções, ajudando na aeração do solo, na dinâmica hídrica e no processo de ciclagem dos nutrientes. Apesar do papel que desempenham na formação da cobertura pedológica, a maior parte dos levantamentos de solo não contempla os agregados biogênicos, por este motivo, demos ênfase especial à descrição destas morfologias. / The focus of this research is the activity of earthworms and their influence on the soil of an Atlantic Plateau hill slope in São Paulo State. Our area of study is surrounded by environmental preservation areas, it has primary forests in good conditions, warm climate and precipitations above 2,000 mm per year. Three different extraction techniques were used for the survey of annelid communities. The collected organisms were identified at the species level and its distribution was analyzed along the topography. We found a variation of earthworm populations in the three sectors of the slope, with the highest densities in the foothills and lower densities in the top. There is an intense activity of these organisms in the soil and they are not equally distributed in the vertical profile, concentrating on a few layers, sometimes in topsoil, sometimes in subsoil. We also observed the presence of exotic species in disturbed areas. The activity of soil fauna changes the morphology (bioaggregation), the physical (macroporosity), and chemical (P, K+, Ca2+, Mg2+ and organic matter dynamics, sum of bases and cation exchange capacity) attributes of soil, affecting many pedological processes. With their feeding and builder ecological behaviors, earthworms create galleries, channels and produce casts, helping in soil aeration, the water dynamics and nutrient cycling processes. Despite the role they play in the formation of soil mantle, most of the ground surveys does not include the biogenic aggregates, therefore, we gave special emphasis on the descriptions of such morphologies.