Cryptococcus neoformans senses CO2 through the carbonic anhydrase Can2 and the adenylyl cyclase Cac1.
Cryptococcus neoformans, a fungal pathogen of humans, causes fatal meningitis in immunocompromised patients. Its virulence is mainly determined by the elaboration of a polysaccharide capsule surrounding its cell wall. During its life, C. neoformans is confronted with and responds to dramatic variations in CO2 concentrations; one important morphological change triggered by the shift from its natural habitat (0.033% CO2) to infected hosts (5% CO2) is the induction of capsule biosynthesis. In cells, CO2 is hydrated to bicarbonate in a spontaneous reaction that is accelerated by carbonic anhydrases. Here we show that C. neoformans contains two beta-class carbonic anhydrases, Can1 and Can2. We further demonstrate that CAN2, but not CAN1, is abundantly expressed and essential for the growth of C. neoformans in its natural environment, where CO2 concentrations are limiting. Structural studies reveal that Can2 forms a homodimer in solution. Our data reveal Can2 to be the main carbonic anhydrase and suggest a physiological role for bicarbonate during C. neoformans growth. Bicarbonate directly activates the C. neoformans Cac1 adenylyl cyclase required for capsule synthesis. We show that this specific activation is optimal at physiological pH.
Mogensen
Estelle Geweiss
EG
Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom.
Janbon
Guilhem
G
Chaloupka
James
J
Steegborn
Clemens
C
Fu
Man Shun
MS
Moyrand
Frédérique
F
Klengel
Torsten
T
Pearson
David S
DS
Geeves
Michael A
MA
Buck
Jochen
J
Levin
Lonny R
LR
Mühlschlegel
Fritz A
FA
D000262:Adenylyl Cyclases / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019470:Biolistics; D002245:Carbon Dioxide / Q000378:metabolism / Q000494:pharmacology*; D002257:Carbonic Anhydrase Inhibitors / Q000494:pharmacology; D002256:Carbonic Anhydrases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D003001:Cloning, Molecular; D003455:Cryptococcus neoformans / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D004926:Escherichia coli; D005016:Ethoxzolamide / Q000494:pharmacology; D017353:Gene Deletion; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D055672:Static Electricity; D040681:Structural Homology, Protein
D002257:Carbonic Anhydrase Inhibitors; D002245:Carbon Dioxide; D002256:Carbonic Anhydrases; D000262:Adenylyl Cyclases; D005016:Ethoxzolamide