title: Novel mechanism coupling cyclic AMP-protein kinase A signaling and golgi trafficking via Gyp1 phosphorylation in polarized growth.
abstract: The cyclic AMP (cAMP)-protein kinase A (PKA) signaling activates virulence expression during hyphal development in the fungal human pathogen Candida albicans. The hyphal growth is characterized by Golgi polarization toward the hyphal tips, which is thought to enhance directional vesicle transport. However, how the hypha-induction signal regulates Golgi polarization is unknown. Gyp1, a Golgi-associated protein and the first GTPase-activating protein (GAP) in the Rab GAP cascade, critically regulates membrane trafficking from the endoplasmic reticulum to the plasma membrane. Here, we report a novel pathway by which the cAMP-PKA signaling triggers Golgi polarization during hyphal growth. We demonstrate that Gyp1 plays a crucial role in actin-dependent Golgi polarization. Hyphal induction activates PKA, which in turn phosphorylates Gyp1. Phosphomimetic mutation of four PKA sites identified by mass spectrometry (Gyp1(4E)) caused strong Gyp1 polarization to hyphal tips, whereas nonphosphorylatable mutations (Gyp1(4A)) abolished it. Gyp1(4E) exhibited enhanced association with the actin motor Myo2, while Gyp1(4A) showed the opposite effect, providing a possible mechanism for Golgi polarization. A GAP-dead Gyp1 (Gyp1(R292K)) showed strong polarization similar to that seen with Gyp1(4E), indicating a role for the GAP activity. Mutating the PKA sites on Gyp1 also impaired the recruitment of a late Golgi marker, Sec7. Furthermore, proper PKA phosphorylation and GAP activity of Gyp1 are required for virulence in mice. We propose that the cAMP-PKA signaling directly targets Gyp1 to promote Golgi polarization in the yeast-to-hypha transition, an event crucial for C. albicans infection.
authors.affiliation: Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore zxhuang@imcb.a-star.edu.sg mcbwangy@imcb.a-star.edu.sg.
authors.forename: Zhen-Xing
authors.initials: ZX
authors.lastname: Huang
authors.affiliation: Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore.
authors.forename: Haitao
authors.initials: H
authors.lastname: Wang
authors.affiliation: Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore.
authors.forename: Yan-Ming
authors.initials: YM
authors.lastname: Wang
authors.affiliation: Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore zxhuang@imcb.a-star.edu.sg mcbwangy@imcb.a-star.edu.sg.
authors.forename: Yue
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000818:Animals; D002176:Candida albicans / Q000201:enzymology* / Q000472:pathogenicity; D002177:Candidiasis / Q000201:enzymology / Q000382:microbiology; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D006056:Golgi Apparatus / Q000201:enzymology*; D025301:Hyphae / Q000201:enzymology / Q000472:pathogenicity; D007668:Kidney / Q000382:microbiology / Q000473:pathology; D051379:Mice; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D015398:Signal Transduction; D014774:Virulence
chemical_list: D005656:Fungal Proteins; D020690:GTPase-Activating Proteins; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases