Role of the Cryptococcus neoformans Copper Acquisition Machinery in lethal meningitis

• Applicant: Dr. Corinna Probst
• Subject Area: Parasitology and Biology of Tropical Infectious Disease Pathogens ; Biochemistry ; Cell Biology
• Term: from 2017 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 350009704

The fungus Cryptococcus neoformans (C. neoformans) is a life threatening fungal pathogen and is responsible for ~650,000 deaths per year worldwide. C. neoformans preferentially infects individuals who are immmunocompromised due to HIV-AIDS, diabetes, cancer chemotherapy or organ transplant recipients who are maintained on immunosuppressive drugs. C. neoformans is acquired through the respiratory route and survival from alveolar macrophage phagocytosis in the lung allows it to disseminate through the bloodstream and cross the blood brain barrier, where it causes lethal meningitis. Copper (Cu) is an essential trace element for many physiological functions in mammals and also in C. neoformans, where it is required for several virulence-related processes such as melanin biogenesis, iron absorption, superoxide detoxification and capsule formation. Recent studies have shown that the ability of C. neoformans to resist Cu toxicity in the phagolysosome of lung macrophages is important for survival, dissemination and virulence. In contrast, the ability of C. neoformans to acquire Cu in brain, through the Ctr1 and Ctr4 high affinity Cu+ transporters, is critical for lethal meningitis. The Cu detoxification genes are activated in response to high Cu, and the Cu acquisition genes activated by low Cu, by the same Cu metalloregulatory transcription factor, Cuf1. My Postdoctoral mentor´s laboratory has recently identified all of the high Cu- or Cu-deficiency-regulated, Cuf1-dependent target genes in C. neoformans and discovered a putative GPI-linked Cu-dependent Lytic Polysaccharide Monooxygenase (LPMO), Bim1, that is strongly activated under Cu deficiency and which plays a critical role in Cu acquisition. Bim1 is liberated into the growth medium and purified Bim1 is able to restore growth to bim1 knockout cells in Cu-deficient medium in a Ctr1 and Ctr4-dependent manner, suggesting a novel role for an LPMO-like protein in Cu acquisition and potentially in fungal meningitis. In this application I outline two specific aims directly relevant to the importance of Cu acquisition in fungal pathogenesis. In one aim, I will validate the novel role for Bim1 in C. neoformans Cu acquisition and decipher its mechanism of action. In the second aim I will ascertain if the Cu acquisition role of Bim1 serves as an important virulence factor for lethal meningitis. I will also test whether mouse models of Wilson Disease (WD), a rare human disease of hepatic and brain Cu overload, or WD carriers that are present at a high frequency, are more susceptible to C. neoformans mediated fungal meningitis. My Postdoctoral research in the Thiele laboratory will explore a novel mechanism in Cu uptake relevant to fungal pathogenesis, equip me with a strong foundation in host-pathogen interactions and will provide a unique training ground to build my expertise to support a career as an independent scientist in an area of great biomedical importance.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Dr. Dennis J. Thiele