TABLE 1

pH signal processing in fungal model organisms and in the main human fungal pathogens

Processing stepFungal species
Aspergillus nidulansSaccharomyces cerevisiaeCandida albicansAspergillus fumigatusCryptococcus neoformans
Sensing
    Cell locationPlasma membranePlasma membranePlasma membranePlasma membraneNot described
    Proteins (orthologues)PalH with 7 TMDs,a PalI with 4 TMDs, PalF arrestin likeDfg16/Rim21(PalH), Rim9 (PalI), Rim8 (PalF)Dfg16/Rim21, Rim9, Rim8PalH, PalFNot described
    TriggerPalH-PalF interaction, PalF phosphorylation and ubiquitination (neutral-alkaline pH dependent)Rim21-Rim8 interaction, Rim8 phosphorylation and ubiquitination (pH independent)Rim21-Rim8 interaction, Rim8 hyperphosphorylation dependent on Rim101 activationNot describedbNot described
Signaling
    Cell locationPlasma membrane, endosomePlasma membrane, endosomePlasma membrane, endosomeNot describedbNot described
    Proteins (orthologues)PalH, PalF, PalC, Vps23 (ESCRT-Ic), Vps32/Vps20, Vps24 (ESCRT-IIIc)Rim21, Rim8, Rim23 (PalC), Vps23, Vps32/Vps20, Vps24Rim21, Rim8, Rim23, Vps32/Vps20Not describedbNot described
    TriggerBinding of ubiquitinated PalF-PalH to PalC and Vps23, PalF-dependent endocytosis of PalH through Vps23 recruitment of Vps32/Vps20Binding of ubiquitinated Rim8-Rim21 to Rim23 and Vps23, Rim8-dependent endocytosis of Rim21 through Vps23 recruitment of Vps32/Vps20/Vps24Interaction of hyperphosphorylated Rim8 with Rim21and Rim101, Rim8-dependent endocytosis of Rim21 through Vps32/Vps20 bindingNot describedNot described
Processing of PacC/Rim101
    Cell locationFirst proteolysis in endosome, second proteolysis in proteasomeSingle proteolysis in endosomeSingle proteolysis in endosomeNot describedbNot described
    ProteinsInteraction of Vps32/Vps20 with PalA, and Vps24 with PalB. First PalB-mediated proteolysis of PacC72 to generate PacC53. Second proteolysis mediated by the proteasomeInteraction of Vps32/Vps20/Vps24 with Rim20, Rim13, and Rim101, Rim13-mediated proteolysis of Rim101Interaction of Vps32 with Rim20, Rim13, and Rim101, Rim13-mediated proteolysis of Rim101 to generate Rim10165Not describedbNot described, but two proteolysis steps dependent on Rim13, Rim20, and cAMP/PKA pathway
    TriggerPacC27 translocation to the nucleusTranslocation to nucleus of Rim101 truncated form corresponding to PacC53Translocation to the nucleus of Rim10165Not describedNot described
Activation
    Cell locationNucleusNucleusNucleusNot describedNot described
    ProteinsBinding of PacC27 to pH responsive genesBinding of truncated Rim101to pH-responsive genesBinding of truncated Rim101to pH-responsive genesNot describedNot described
Regulation
    ProteinsPacCNot describedRim8, Rim101Not describedNot described
    TriggerAutogenous PacC mediated activationNot describedRim101-mediated repression and degradation of Rim8 and autogenous Rim101-mediated activationNot describedNot described
  • a TMD, transmembrane domain.

  • b Thought to be highly similar to that in A. nidulans.

  • c Endosomal sorting complex required for transport.