Schizosaccharomyces pombe Git1 is a C2-domain protein required for glucose activation of adenylate cyclase.
Schizosaccharomyces pombe senses environmental glucose through a cAMP-signaling pathway, activating cAMP-dependent protein kinase A (PKA). This requires nine git (glucose insensitive transcription) genes that encode adenylate cyclase, the PKA catalytic subunit, and seven "upstream" proteins required for glucose-triggered adenylate cyclase activation, including three heterotrimeric G-protein subunits and its associated receptor. We describe here the cloning and characterization of the git1+ gene. Git1 is distantly related to a small group of uncharacterized fungal proteins, including a second S. pombe protein that is not functionally redundant with Git1, as well as to members of the UNC-13/Munc13 protein family. Mutations in git1+ demonstrate functional roles for the two most highly conserved regions of the protein, the C2 domain and the MHD2 Munc homology domain. Cells lacking Git1 are viable, but display phenotypes associated with cAMP-signaling defects, even in strains expressing a mutationally activated G alpha-subunit, which activates adenylate cyclase. These cells possess reduced basal cAMP levels and fail to mount a cAMP response to glucose. In addition, Git1 and adenylate cyclase physically interact and partially colocalize in the cell. Thus, Git1 is a critical component of the S. pombe glucose/cAMP pathway.
Biology Department, Boston College, Chestnut Hill, Massachusetts 02467, USA.
Richard S
RS
Kao
Eric
E
Morreale
Lili
L
Wang
F Douglas
FD
Ivey
Charles S
CS
Hoffman
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D044388:GTP-Binding Protein gamma Subunits / Q000737:chemistry* / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal / Q000235:genetics; D005816:Genetic Complementation Test; D005947:Glucose / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012568:Schizosaccharomyces / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry* / Q000378:metabolism*; D016415:Sequence Alignment; D013172:Spores, Fungal / Q000502:physiology; D013489:Suppression, Genetic
D044388:GTP-Binding Protein gamma Subunits; D029702:Schizosaccharomyces pombe Proteins; C427234:git11 protein, S pombe; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D005947:Glucose