Glioblastomas (GBMs) are resistant to current therapy protocols and identification of molecules that target these tumors is crucial. Interaction of secreted heat-shock protein 70 (Hsp70)-Hsp90-organizing protein (HOP) with cellular prion protein (PrP(C)) triggers a large number of trophic effects in the nervous system. We found that both PrP(C) and HOP are highly expressed in human GBM samples relative to non-tumoral tissue or astrocytoma grades I-III. High levels of PrP(C) and HOP were associated with greater GBM proliferation and lower patient survival. HOP-PrP(C) binding increased GBM proliferation in vitro via phosphatidylinositide 3-kinase and extracellular-signal-regulated kinase pathways, and a HOP peptide mimicking the PrP(C) binding site (HOP230-245) abrogates this effect. PrP(C) knockdown impaired tumor growth and increased survival of mice with tumors. In mice, intratumor delivery of HOP230-245 peptide impaired proliferation and promoted apoptosis of GBM cells. In addition, treatment with HOP230-245 peptide inhibited tumor growth, maintained cognitive performance and improved survival. Thus, together, the present results indicate that interfering with PrP(C)-HOP engagement is a promising approach for GBM therapy.

Prion protein modulates many cellular functions including the secretion of trophic factors by astrocytes. Some of these factors are found in exosomes, which are formed within multivesicular bodies (MVBs) and secreted into the extracellular space to modulate cell-cell communication. The mechanisms underlying exosome biogenesis were not completely deciphered. Here, we demonstrate that primary cultures of astrocytes and fibroblasts from prnp-null mice secreted lower levels of exosomes than wild-type cells. Furthermore, prnp-null astrocytes exhibited reduced MVB formation and increased autophagosome formation. The reconstitution of PRNP expression at the cell membrane restored exosome secretion in PRNP-deficient astrocytes, whereas macroautophagy/autophagy inhibition via BECN1 depletion reestablished exosome release in these cells. Moreover, the PRNP octapeptide repeat domain was necessary to promote exosome secretion and to impair the formation of the CAV1-dependent ATG12-ATG5 cytoplasmic complex that drives autophagosome formation. Accordingly, higher levels of CAV1 were found in lipid raft domains instead of in the cytoplasm in prnp-null cells. Collectively, these findings demonstrate that PRNP supports CAV1-suppressed autophagy to protect MVBs from sequestration into phagophores, thus facilitating exosome secretion.

Stress-inducible phosphoprotein 1 (STI1), a cochaperone for Hsp90, has been shown to regulate multiple pathways in astrocytes, but its contributions to cellular stress responses are not fully understood. We show that in response to irradiation-mediated DNA damage stress STI1 accumulates in the nucleus of astrocytes. Also, STI1 haploinsufficiency decreases astrocyte survival after irradiation. Using yeast two-hybrid screenings we identified several nuclear proteins as STI1 interactors. Overexpression of one of these interactors, PIAS1, seems to be specifically involved in STI1 nuclear retention and in directing STI1 and Hsp90 to specific sub-nuclear regions. PIAS1 and STI1 co-immunoprecipitate and PIAS1 can function as an E3 SUMO ligase for STI. Using mass spectrometry we identified five SUMOylation sites in STI1. A STI1 mutant lacking these five sites is not SUMOylated, but still accumulates in the nucleus in response to increased expression of PIAS1, suggesting the possibility that a direct interaction with PIAS1 could be responsible for STI1 nuclear retention. To test this possibility, we mapped the interaction sites between PIAS1 and STI1 using yeast-two hybrid assays and surface plasmon resonance and found that a large domain in the N-terminal region of STI1 interacts with high affinity with amino acids 450-480 of PIAS1. Knockdown of PIAS1 in astrocytes impairs the accumulation of nuclear STI1 in response to irradiation. Moreover, a PIAS1 mutant lacking the STI1 binding site is unable to increase STI1 nuclear retention. Interestingly, in human glioblastoma multiforme PIAS1 expression is increased and we found a significant correlation between increased PIAS1 expression and STI1 nuclear localization. These experiments provide evidence that direct interaction between STI1 and PIAS1 is involved in the accumulation of nuclear STI1. This retention mechanism could facilitate nuclear chaperone activity.

SummaryTissue microarray technology enables us to evaluate the pattern of protein expression in large numbers of samples. However, manual data acquisition and analysis still represent a challenge because they are subjective and time-consuming. Automated analysis may thus increase the speed and reproducibility of evaluation. However, the reliability of automated analysis systems should be independently evaluated. Herein, the expression of phosphorylated AKT and mTOR was determined by ScanScope XT (Aperio; Vista, CA) and ACIS III (Dako; Glostrup, Denmark) and compared with the manual analysis by two observers. The percentage of labeled pixels or nuclei analysis had a good correlation between human observers and automated systems (κ = 0.855 and 0.879 for ScanScope vs. observers and κ = 0.765 and 0.793 for ACIS III vs. observers). The intensity of labeling determined by ScanScope was also correlated with that found by the human observers (correlation index of 0.946 and 0.851 for pAKT and 0.851 and 0.875 for pmTOR). However, the correlation between ACIS III and human observation varied for labeling intensity and was considered poor in some cases (correlation index of 0.718 and 0.680 for pAKT and 0.223 and 0.225 for pmTOR). Thus, the percentage of positive pixels or nuclei determination was satisfactorily performed by both systems; however, labeling intensity was better identified by ScanScope XT. (J Histochem Cytochem 61:272-282, 2013)

The mammalian target of rapamycin (mTOR) binds to several protein partners and forms two complexes, termed mTOR complexes 1 and 2 (mTORC1/2), that differ in components, substrates, and regulation. mTORC2 contains the protein Rapamycin-insensitive companion of mTOR (RICTOR); phosphorylates kinases of the AGC family, such as Akt; and controls the cytoskeleton. Even though the regulation of mTORC2 activity remains poorly understood, the hyperactivation of this signaling pathway has been shown to contribute to the oncogenic properties of gliomas in experimental models. In this work, we evaluated expression and phosphorylation of Akt, and expression of RICTOR and Ki-67 in 195 human astrocytomas of different grades (38 cases of grade I, 49 grade II, 15 grade III, and 93 grade IV) and 30 normal brains. Expression and phosphorylation of Akt increased with histological grade and correlated with a worse overall survival in glioblastomas (GBMs). RICTOR was overexpressed in grade I and II astrocytomas and demonstrated a shift to nuclear localization in GBMs. Nuclear RICTOR was associated to increased proliferation in GBMs. Our results point to an increase in total and phosphorylated Akt in high-grade gliomas and to a possible role of RICTOR in proliferations of high-grade GBM cells.

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Resumo O sequestro pulmonar refere-se à anomalia congênita definida por massa de parênquima pulmonar não funcionante. É dividido pela existência de envoltório pleural próprio em intralobar, representando cerca de 75% dos casos, ou extralobar, responsável pelos 25% restantes. O diagnóstico é feito através de radiografia e confirmado com tomografia computadorizada, ressonância nuclear magnética e arteriografia. Tradicionalmente, o tratamento proposto é cirúrgico, mas a técnica endovascular tem apresentado bons resultados. É relatado o caso de uma mulher, 29 anos, com quadro clínico de pneumonias de repetição desde os 5 anos. A tomografia de tórax revelou malformação vascular em região inferior de pulmão direito. O tratamento vascular foi realizado através de embolização do ramo anômalo.