Yonsei University · Medicine
Professor Yong‐Sun Bahn's research lab focuses on the molecular mechanisms underlying fungal pathogenesis, particularly in the human pathogenic yeast *Cryptococcus neoformans*. The lab investigates conserved signaling pathways—such as the Pbs2-Hog1 MAPK cascade, cAMP signaling, and the unfolded protein response (UPR)—that regulate stress responses, morphological transitions, and virulence. By integrating molecular genetics, cell biology, and comparative genomics, the lab uncovers how these pathways have evolved to support fungal survival and pathogenicity in diverse environments. A central theme is understanding how fungal pathogens adapt to host environments through signaling network rewiring and evolutionary innovation.
Figures are computed from collected data and may differ slightly.
The human pathogenic fungus Cryptococcus neoformans has diverged from a common ancestor into three biologically distinct varieties or sibling species over the past 10-40 million years. During evolution of these divergent forms, serotype A C. neoformans var. grubii has emerged as the most virulent and cosmopolitan pathogenic clade. Therefore, understanding how serotype A C. neoformans is distinguished from less successful pathogenic serotypes will provide insights into the evolution of fungal vir
The stress-activated mitogen-activated protein kinase (MAPK) pathway is widely used by eukaryotic organisms as a central conduit via which cellular responses to the environment effect growth and differentiation. The basidiomycetous human fungal pathogen Cryptococcus neoformans uniquely uses the stress-activated Pbs2-Hog1 MAPK system to govern a plethora of cellular events, including stress responses, drug sensitivity, sexual reproduction, and virulence. Here, we characterized a fungal “two-compo
30).On the right side are diagrams of known fungal sensor kinases, which were generated by the MacVector software.Each domain was identified by the comparative fungal genomics platform (http://cfgp.snu.ac.kr) and
In response to a wide variety of environmental stimuli, the opportunistic fungal pathogen Candida albicans exits the budding cycle, producing germ tubes and hyphae concomitant with expression of virulence genes, such as that encoding hyphal wall protein 1 (HWP1). Biochemical studies implicate cyclic AMP (cAMP) increases in promoting bud-hypha transitions, but genetic evidence relating genes that control cAMP levels to bud-hypha transitions has not been reported. Adenylate cyclase-associated prot
In eukaryotic cells, the unfolded protein response (UPR) pathway plays a crucial role in cellular homeostasis of the endoplasmic reticulum (ER) during exposure to diverse environmental conditions that cause ER stress. Here we report that the human fungal pathogen Cryptococcus neoformans has evolved a unique UPR pathway composed of an evolutionarily conserved Ire1 protein kinase and a novel bZIP transcription factor encoded by HXL1 (HAC1 and XBP1-Like gene 1). C. neoformans HXL1 encodes a protein
The evolutionarily conserved cyclic AMP (cAMP) signaling pathway controls cell functions in response to environmental cues in organisms as diverse as yeast and mammals. In the basidiomycetous human pathogenic fungus Cryptococcus neoformans, the cAMP pathway governs virulence and morphological differentiation. Here we identified and characterized adenylyl cyclase-associated protein, Aca1, which functions in parallel with the Galpha subunit Gpa1 to control the adenylyl cyclase (Cac1). Aca1 interac
Frequent interconversion between yeasts, pseudohyphae and true hyphae is a hallmark of Candida albicans growth in mammalian tissues. The requirement for transient CAP1-dependent pulses of cAMP for generating true hyphae, Hwp1 and virulence raises questions about the role of yeast and pseudohyphal forms in the pathogenesis of candidiasis. In this study, hyperfilamentous mutants, limited in their capacity to produce buds, were generated by disrupting the high-affinity phosphodiesterase gene PDE2.
Sensing, responding, and adapting to the surrounding environment are crucial for all living organisms to survive, proliferate, and differentiate in their biological niches. This ability is also essential for Cryptococcus neoformans and its sibling species Cryptococcus gattii, as these pathogens have saprobic and parasitic life cycles in natural and animal host environments. The ability of Cryptococcus to cause fatal meningoencephalitis is highly related to its capability to remodel and optimize
The cyclic AMP (cAMP) pathway plays a central role in the growth, differentiation, and virulence of pathogenic fungi, including Cryptococcus neoformans. Three upstream signaling regulators of adenylyl cyclase (Cac1), Ras, Aca1, and Gpa1, have been demonstrated to control the cAMP pathway in C. neoformans, but their functional relationship remains elusive. We performed a genome-wide transcriptome analysis with a DNA microarray using the ras1Delta, gpa1Delta, cac1Delta, aca1Delta, and pka1Delta pk
Organisms living in extreme environments have evolved a wide range of survival strategies by changing biochemical and physiological features depending on their biological niches. Interestingly, organisms exhibiting high radiation resistance have been discovered in the three domains of life (Bacteria, Archaea, and Eukarya), even though a naturally radiationintensive environment has not been found. To counteract the deleterious effects caused by radiation exposure, radiation- resistant organisms e
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