Petra Balogh

The Role of Endocytic Pathways in TGF-β Signaling

Transforming growth factor β (TGF-β) superfamily consists of numerous cytokins that regulate various cellular processes. TGF-β, the prototype of the family, signals through its cell surface serine/threonin kinase receptors and besides its role in cell differentiation, migration, adhesion etc. it is also able to induce epithelial-mesenchymal (EMT) transition via both Smad- pathway and MAPK- pathway. Among the different types of epithelial-mesenchymal transition, type II that is described to be associated with wound healing, tissue regeneration, organ fibrosis and is induced upon inflammatory stimuli. It can be triggered by secretion of growth factors such as TGF-β, EGF. Different endocytic routes are used for the internalization of TGF-β ligand and its receptors and these pathways can control the activity of downstream events. Internalization via clathrin-coated vesicles promotes the signaling while the caveola-mediated endocytosis plays important role in the termination of the events, although the steps of the latter event are less clear. The early endosome is considered a clue compartment in promoting the signaling. Recently published data suggest that the early endosome plays crucial role in the termination of the TGFβ signaling as well. It is not only maintain a special environment for the effective signaling but can direct the internalized cargos towards degradative pathways (multivesicular bodies, lysosomes).

Estrogen Receptor Alpha Is Expressed in Mesenteric Mesothelial Cells and Is Internalized in Caveolae upon Freund's Adjuvant Treatment

Transformation of epithelial cells into connective tissue cells (epithelial-mesenchymal transition, EMT) is a complex mechanism involved in tumor metastasis, and in normal embryogenesis, while type II EMT is mainly associated with inflammatory events and tissue regenaration. In this study we examined type II EMT at the ultrastructural and molecular level during the inflammatory process induced by Freunds adjuvant treatment in rat mesenteric mesothelial cells. We found that upon the inflammatory stimulus mesothelial cells lost contact with the basal lamina and with each other, and were transformed into spindle-shaped cells. These morphological changes were accompanied by release of interleukins IL-1alpha, -1beta and IL-6 and by secretion of transforming growth factor beta (TGF-β) into the peritoneal cavity. Mesothelial cells also expressed estrogen receptor alpha (ER-α) as shown by immunolabeling at the light and electron microscopical levels, as well as by quantitative RT-PCR. The mRNA level of ER-α showed an inverse correlation with the secretion of TGF-β. At the cellular and subcellular levels ER-α was colocalized with the coat protein caveolin-1 and was found in the plasma membrane of mesothelial cells, in caveolae close to multivesicular bodies (MVBs) or in the membrane of these organelles, suggesting that ER-α is internalized via caveola-mediated endocytosis during inflammation. We found asymmetric, thickened, electron dense areas on the limiting membrane of MVBs (MVB plaques) indicating that these sites may serve as platforms for collecting and organizing regulatory proteins. Our morphological observations and biochemical data can contribute to form a potential model whereby ER-α and its caveola-mediated endocytosis might play role in TGF-β induced type II EMT in vivo.

Mesothelial cells can detach from the mesentery and differentiate into macrophage-like cells

Katz S, Balogh P, Kiss AL. Mesothelial cells can detach from the mesentery and differentiate into macrophage‐like cells. APMIS 2011; 119: 782–93.

Epithelial-to-mesenchymal transition induced by Freund's adjuvant treatment in rat mesothelial cells: a morphological and immunocytochemical study.

Intraperitoneal injection of Freund’s adjuvant induces acute peritonitis. By the time of the Freund’s adjuvant treatment the flat, simple squamous epithelial cells became rounded, cuboidal shaped, many of them have lost their connection with the neighbouring cells and detached from the basement membrane. The macrophage markers’ (ED1, OX43 and CD68) expression also increased in the mesothelial cells and more mesothelin and anti-ED1 double-labelled cells were found freely present close to the surface. The cytokeratin expression of the mesothelial cells has gradually decreased. At the 5th day of the inflammation practically there was no cytokeratin labelling present in the mesothelial cells and the mesothelin expression has significantly decreased. Parallel to this mesothelial cells started to express vimentin, a characteristic mesenchymal intermediate filament protein indicating that they gradually lost their epithelial character and gained mesenchymal phenotype. These results strongly suggest that under the effect of Freund’s adjuvant treatment (inflammation) mesothelial cells can undergo epithelial-to-mesenchymal transition and differentiate into phagocytotic (macrophage-like) cells. Studying the caveolae/caveolin-1 on the plasma membrane of mesothelial cells we found that the Freund’s adjuvant treatment has changed the cellular distribution of caveolin-1: as the inflammation progressed strong caveolin-1 labelling was found inside of the cytoplasm (in perinuclear localization) indicating that inflammation induced the caveolae internalization. These results indicate that caveolae/caveolin-1 might play important regulatory role in signal transduction leading to trasdifferentiation.

The subcellular compartmentalization of TGFβ-RII and the dynamics of endosomal formation during the signaling events: An in vivo study on rat mesothelial cells

We previously showed that intraperitoneal administration of Freunds adjuvant treatment resulted in acute peritonitis and TGF-β was found to be one of the main organizers of the subsequent EMT in mesothelial cells. In the present study, we investigated whether TGF-β signaling molecules are present in mesothelial cells and how their compartmentalization pattern changes with the dynamics of inflammatory events in vivo. In addition, we tried to evaluate the turnover of endosomal compartments concomitant with the internalization of signaling molecules and examine whether caveola-mediated internalization might play a role in the termination of TGF-β signaling. Using immunocytochemical approach, we could detect TβRII in EEA1 positive compartments and as the inflammation progressed, at D3, the receptor appeared in caveolin-1 positive intracellular structures as well. The latter event was accompanied by the appearance of negative regulatory protein, Smad7 in caveolae. We also found EEA1 and caveolin-1 double positive vesicular structures that were corresponded to forming MVBs affirmed by our immuno-electron microscopical results. Fine structural, morphometric and immunoblot analysis proved that Cd63 positive multivesicular body (MVB) formation was significantly increased by D3 and the IP results confirmed that TβRII as well as caveolin-1 were strongly associated with these endosomal compartments at this time. In contrast, by the termination of inflammation, by D5, caveolin-1 was found to be associated with late endosomal marker, Rab7 and entirely degraded from the system. Despite the limitations of an in vivo system, our results provide both morphological and biochemical data about the endosomal compartments involved in the internalization of TβRII upon inflammatory stimuli. Furthermore, our study implies the possible role of caveola-mediated endocytosis in the attenuation of TGF-β signaling and highlight the significance of endosomal compartments via which caveolae might meet the classical endocytic pathway under in vivo inflammatory conditions.

Expression of G protein-coupled oestrogen receptor in melanoma and in pregnancy-associated melanoma

The hormone sensitivity of melanoma and the role of ‘classical’ oestrogen receptor (ER) α and β in tumour progression have been intensively studied with rather contradictory results. The presence of ‘non‐classical’ G protein‐coupled oestrogen receptor (GPER) has not been investigated on human melanoma tissues.

Autophagy may contribute to the recovery of rat mesothelium following acute inflammation in vivo

Following Freund’s adjuvant-induced acute inflammation, the regeneration of rat mesothelium is accompanied by the reduction of cell organelles. The aim of the present study is to test whether autophagy may play a role in the recovery process of mesothelial cells by eliminating accumulated cell organelles and also to investigate the presence of potential inducers and molecular transmitters of the process. Control and treated (from day 2 to day 11; D2–D11) mesothelial cells (n = 16 samples/group) obtained from male rats were isolated and phenotypically characterized. Morphological studies included light and electron microscopy. Biochemical studies performed on tissue samples as well as isolated cells were used to evaluate the dynamics of autophagy and also to detect the expression levels of TNF-α, LC3B, estrogen receptors (ER-α and GPR30) and Erk1/2. Gene expression was measured by individual Taqman assays on quantitative RT-PCR. Protein expression study was performed by Western blotting and immunolabeling. Estradiol concentration was measured both in peritoneal fluid and plasma samples in control and treated animals (n = 3–10 animals per group). Our conventional electron microscopic and morphometric results showed a progressive autophagosome formation with a peak by the termination of inflammation (D5). Subsequently, autophagolysosome formation dominated between D6 and D8 with a concomitant expression of LC3B proved by immunoblotting. We further observed the reduction of cell compartments by D11 parallel with the morphological restitution of mesothelium. Estradiol showed a sustained level in the peritoneal fluid but not in plasma samples between D3 and D11 compared to levels obtained from untreated animals. The mRNA expression of TNF-α was increased between D2 and D11 compared to control. Western blot analysis showed a constitutive expression of GPR30, while ER-α could not be detected between D6 and D11. Erk1/2 was activated by phosphorylation with a peak at D6. Considering our present in vivo results, we hypothesize that the facilitated autophagy might play an important role in the removal of cytoplasmic organelles during the recovery of mesothelium, while our results also suggest that the detected peritoneal estradiol as well as TNF-α may contribute to this process.

Membrane-Bound Estrogen Receptor Alpha Initiated Signaling is Dynamin Dependent in MCF-7 Cells

Although membrane-associated estrogen receptors (mERs) have been known to play important role in steroid induced signal transmission, we still know little about their function in the estrogen induced proliferation of breast cancer cells. In our current work we tried to separate membrane initiated estrogen receptor (ERα,) signaling from the overall estrogenic effect in MCF7 breast carcinoma cells. Re-analyzing expression data from multiple microarray experiments, we selected a set of key regulatory genes involved in proliferation regulation and estrogen signaling. Our quantitative real time-PCR results confirmed that the selective membrane receptor agonist, estrogen-BSA induces similarly pronounced expression changes regarding these genes as 17β-estradiol. Our light and electronmicroscopical studies revealed that the membrane-bound form of classical estrogen receptor alpha is internalized after ligand binding via dynamin dependent, caveola-mediated endocytosis. Inhibition of this internalization with dynamin inhibitor, dynasore practically abolished the regulatory effect of E2-BSA, suggesting that interaction and internalization with the scaffold protein is necessary for effective signaling. The physiological role of plasma membrane estrogen receptor alpha is intensively studied, yet there are still several aspects of it to be resolved. The dynamin-dependent, ligand mediated internalization of mERs seems to play an important role in estrogen signaling. Our results may serve as another example how membrane initiated and nuclear receptor signaling well-orchestrated is and form an integrated system.

Primary alveolar rhabdomyosarcoma of the bone: two cases and review of the literature

BackgroundRhabdomyosarcoma (RMS) is a malignant tumor of mesenchymal origin and comprises the largest category of soft-tissue sarcomas both in children and adolescents. From a pediatric oncology point of view, RMS has traditionally been classified into alveolar (ARMS) and embryonal (ERMS) subtypes. The anatomical localization of the tumor may vary, but commonly involve the head/neck regions, male and female urogenital tract or the trunk and extremities.Case presentationHere, we report two challenging cases involving 17- and 9-years-olds males where diffuse and multiplex bone lesions suggested either a hematological disease or a primary bone tumor (mesenchymal chondrosarcoma). Biopsies, proved a massive infiltration of the bone marrow cavity with rhabdomyosarcoma. In both cases, the ARMS subtype was confirmed using FOXO1 break-apart probes (FISH). Radiological examination could not identify primary soft tissue component in any localization at the time of diagnosis in either cases.ConclusionsPrimary alveolar rhabdomyosarcoma of the bone as a subtype of ARMS, seems to be a distinct clinico-pathological entity with challenging diagnostic difficulties and different, yet better, biological behavior in comparison to soft tissue ARMS. However, it is difficult to be characterized or predict its prognosis and long-term survival as only sporadic cases (four) were reported so far.