Fungal cells change shape in response to environmental stimuli, and these morphogenic transitions drive pathogenesis and niche adaptation. For example, dimorphic fungi switch between yeast and hyphae in response to changing temperature. The basidiomycete Cryptococcus neoformans undergoes an unusual morphogenetic transition in the host lung from haploid yeast to large, highly polyploid cells termed Titan cells. Titan cells influence fungal interaction with host cells, including through increased drug resistance, altered cell size, and altered Pathogen Associated Molecular Pattern exposure. Despite the important role these cells play in pathogenesis, understanding the environmental stimuli that drive the morphological transition, and the molecular mechanisms underlying their unique biology, has been hampered by the lack of a reproducible in vitro induction system. Here we demonstrate reproducible in vitro Titan cell induction in response to environmental stimuli consistent with the host lung. In vitro Titan cells exhibit all the properties of in vivo generated Titan cells, the current gold standard, including altered capsule, cell wall, size, high mother cell ploidy, and aneuploid progeny. We identify the bacterial peptidoglycan subunit Muramyl Dipeptide as a serum compound associated with shift in cell size and ploidy, and demonstrate the capacity of bronchial lavage fluid and bacterial co-culture to induce Titanisation. Additionally, we demonstrate the capacity of our assay to identify established (cAMP/PKA) and previously undescribed (USV101) regulators of Titanisation in vitro. Finally, we investigate the Titanisation capacity of clinical isolates and their impact on disease outcome. Together, these findings provide new insight into the environmental stimuli and molecular mechanisms underlying the yeast-to-Titan transition and establish an essential in vitro model for the future characterization of this important morphotype.

Purpose of Review During infection, the human fungal pathogen Cryptococcus neoformans undergoes an unusual change in size, from small haploid yeast to large polyploid Titan cells. This transition is now well recognized as a virulence factor, but significant questions remain about how Titanisation is regulated and how it influences disease progression. Progress has been impeded by the lack of an in vitro model for the yeast-to-Titan transition, a challenge that was recently overcome by three independent groups. Recent Findings Here, we review Titanization in the context of patient samples and animal models and set the stage for three new reports describing in vitro Titan cell induction assays. We compare and contrast key findings, place them in the broader research context, and identify areas of further interest. Summary New in vitro models will allow pressing questions about molecular mechanisms driving the yeast-to-Titan transition and their influence on drug resistance and pathogenesis to be addressed.

A bacterial endosymbiont of the fungus Rhizopus microsporus drives phagocyte evasion and opportunistic virulence Highlights d Bacterial endosymbionts protect fungal spores from phagocytes d A secreted factor blocks growth and killing by environmental amoebas d Endosymbionts improve fungal stress resistance d Endosymbiosis also allows the evasion of vertebrate immune cells and virulence in vivo

Increased expression of Golgi phosphoprotein 3 (GOLPH3) has been reported to be associated with several types of human cancer. Patient-derived cancer xenograft models have demonstrated great potential in preclinical studies. In the present study, the link between GOLPH3 expression and survival was examined in patients with non-small cell lung cancer (NSCLC). Patient-derived lung cancer xenograft models were established with two different methods. Lastly, the association between GOLPH3 expression and establishment of the xenograft models was explored. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and immunohistochemistry analysis were used to examine GOLPH3 expression in 60 NSCLC tissues and matched adjacent non-cancerous tissues (ANT). In addition, tumor pieces from the 60 NSCLC tissues were implanted in the subcutaneous layer and in the subrenal kidney capsule of nude mice. RT-qPCR, histopathology and immunohistochemistry were used to confirm the human origin of the xenograft tumors. RT-qPCR was also used to research the mutation status of GOLPH3 in the xenograft tumors. The results demonstrated that NSCLC tissues had higher expression of GOLPH3, at the mRNA and protein level, compared with ANT. High expression of GOLPH3 correlated with poor survival in patients with NSCLC. Successful engraftment was established for 27 tissues in the subrenal kidney capsule and for 16 in the subcutaneous layer of nude mice. The subrenal kidney capsule group demonstrated significantly higher engraftment rates than the subcutaneous layer group. In addition, higher GOLPH3 expression in the tumor tissues was significantly correlated with higher engraftment rates in mice. In both groups, few xenografts lost the GOLPH3 mutation. In summary, GOLPH3 may be an important diagnosis and prognosis indicator in patients with NSCLC. The genotype and phenotype of the xenograft tumors derived from patient lung cancer tissues exhibited significant similarities to the originating primary tumors. High GOLPH3 expression may promote the successful establishment of xenograft models for NSCLC.

The pannexin-1 (Panx1) channel (often referred to as the Panx1 hemichannel) is a large-conductance channel in the plasma membrane of many mammalian cells. While opening of the channel is potentially detrimental to the cell, little is known about how it is regulated under physiological conditions. Here we show that stomatin inhibited Panx1 channel activity. In transfected HEK-293 cells, stomatin reduced Panx1-mediated whole-cell currents without altering either the total or membrane surface Panx1 protein expression. Stomatin coimmunoprecipitated with full-length Panx1 as well as a Panx1 fragment containing the fourth membrane-spanning domain and the cytosolic carboxyl terminal. The inhibitory effect of stomatin on Panx1-mediated whole-cell currents was abolished by truncating Panx1 at a site in the cytosolic carboxyl terminal. In primary culture of mouse astrocytes, inhibition of endogenous stomatin expression by small interfering RNA enhanced Panx1-mediated outward whole-cell currents. These observations suggest that stomatin may play important roles in astrocytes and other cells by interacting with Panx1 carboxyl terminal to limit channel opening.