Selection of axial growth sites in yeast requires Axl2p, a novel plasma membrane glycoprotein.
Spa2p and Cdc10p both participate in bud site selection and cell morphogenesis in yeast, and spa2delta cdc10-10 cells are inviable. To identify additional components important for these processes in yeast, a colony-sectoring assay was used to isolate high-copy suppressors of the spa2delda cdc10-10 lethality. One such gene, AXL2, has been characterized in detail. axl2 cells are defective in bud site selection in haploid cells and bud in a bipolar fashion. Genetic analysis indicates that AXL2 falls into the same epistasis group as BUD3. Axl2p is predicted to be a type I transmembrane protein. Tunicamycin treatment experiments, biochemical fractionation and extraction experiments, and proteinase K protection experiments collectively indicate that Axl2p is an integral membrane glycoprotein at the plasma membrane. Indirect immunofluorescence experiments using either Axl2p tagged with three copies of a hemagglutinin epitope or high-copy AXL2 and anti-Axl2p antibodies reveal a unique localization pattern for Axl2p. The protein is present as a patch at the incipient bud site and in emerging buds, and at the bud periphery in small-budded cells. In cells containing medium-sized or large buds, Axl2p is located as a ring at the neck. Thus, Axl2p is a novel membrane protein critical for selecting proper growth sites in yeast. We suggest that Axl2p acts as an anchor in the plasma membrane that helps direct new growth components and/or polarity establishment components to the cortical axial budding site.
Roemer
T
T
Department of Biology, Yale University, New Haven, Connecticut 96520, USA.
Madden
K
K
Chang
J
J
Snyder
M
M
D000595:Amino Acid Sequence; D001483:Base Sequence; D002451:Cell Compartmentation; D002455:Cell Division / Q000235:genetics; D002458:Cell Fractionation; D002462:Cell Membrane / Q000235:genetics / Q000502:physiology*; D016764:Cell Polarity / Q000235:genetics*; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D020690:GTPase-Activating Proteins; D017353:Gene Deletion; D005800:Genes, Fungal; D016153:Genes, Suppressor; D006238:Haploidy; D047908:Intracellular Signaling Peptides and Proteins; D008074:Lipoproteins; D000072235:Mating Factor; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010455:Peptides; D010675:Pheromones; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000254:growth & development*; D029701:Saccharomyces cerevisiae Proteins; D017422:Sequence Analysis, DNA
C098775:Axl2 protein, S cerevisiae; D005656:Fungal Proteins; D020690:GTPase-Activating Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008074:Lipoproteins; C095063:MFA2 protein, S cerevisiae; C076360:MSB2 protein, S cerevisiae; D008562:Membrane Glycoproteins; D010455:Peptides; D010675:Pheromones; D029701:Saccharomyces cerevisiae Proteins; D000072235:Mating Factor