TABLE 1.
pH signal processing in fungal model organisms and in the main human fungal pathogens
| Processing step | Fungal species |
||||
|---|---|---|---|---|---|
| Aspergillus nidulans | Saccharomyces cerevisiae | Candida albicans | Aspergillus fumigatus | Cryptococcus neoformans | |
| Sensing | |||||
| Cell location | Plasma membrane | Plasma membrane | Plasma membrane | Plasma membrane | Not described |
| Proteins (orthologues) | PalH with 7 TMDs,a PalI with 4 TMDs, PalF arrestin like | Dfg16/Rim21(PalH), Rim9 (PalI), Rim8 (PalF) | Dfg16/Rim21, Rim9, Rim8 | PalH, PalF | Not described |
| Trigger | PalH-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 activation | Not describedb | Not described |
| Signaling | |||||
| Cell location | Plasma membrane, endosome | Plasma membrane, endosome | Plasma membrane, endosome | Not describedb | Not described |
| Proteins (orthologues) | PalH, PalF, PalC, Vps23 (ESCRT-Ic), Vps32/Vps20, Vps24 (ESCRT-IIIc) | Rim21, Rim8, Rim23 (PalC), Vps23, Vps32/Vps20, Vps24 | Rim21, Rim8, Rim23, Vps32/Vps20 | Not describedb | Not described |
| Trigger | Binding of ubiquitinated PalF-PalH to PalC and Vps23, PalF-dependent endocytosis of PalH through Vps23 recruitment of Vps32/Vps20 | Binding of ubiquitinated Rim8-Rim21 to Rim23 and Vps23, Rim8-dependent endocytosis of Rim21 through Vps23 recruitment of Vps32/Vps20/Vps24 | Interaction of hyperphosphorylated Rim8 with Rim21and Rim101, Rim8-dependent endocytosis of Rim21 through Vps32/Vps20 binding | Not described | Not described |
| Processing of PacC/Rim101 | |||||
| Cell location | First proteolysis in endosome, second proteolysis in proteasome | Single proteolysis in endosome | Single proteolysis in endosome | Not describedb | Not described |
| Proteins | Interaction of Vps32/Vps20 with PalA, and Vps24 with PalB. First PalB-mediated proteolysis of PacC72 to generate PacC53. Second proteolysis mediated by the proteasome | Interaction of Vps32/Vps20/Vps24 with Rim20, Rim13, and Rim101, Rim13-mediated proteolysis of Rim101 | Interaction of Vps32 with Rim20, Rim13, and Rim101, Rim13-mediated proteolysis of Rim101 to generate Rim10165 | Not describedb | Not described, but two proteolysis steps dependent on Rim13, Rim20, and cAMP/PKA pathway |
| Trigger | PacC27 translocation to the nucleus | Translocation to nucleus of Rim101 truncated form corresponding to PacC53 | Translocation to the nucleus of Rim10165 | Not described | Not described |
| Activation | |||||
| Cell location | Nucleus | Nucleus | Nucleus | Not described | Not described |
| Proteins | Binding of PacC27 to pH responsive genes | Binding of truncated Rim101to pH-responsive genes | Binding of truncated Rim101to pH-responsive genes | Not described | Not described |
| Regulation | |||||
| Proteins | PacC | Not described | Rim8, Rim101 | Not described | Not described |
| Trigger | Autogenous PacC mediated activation | Not described | Rim101-mediated repression and degradation of Rim8 and autogenous Rim101-mediated activation | Not described | Not described |
a
TMD, transmembrane domain.
b
Thought to be highly similar to that in A. nidulans.
c
Endosomal sorting complex required for transport.