High impact information on SPBC4.06

• Precursor to the secretory protein acid phosphatase accumulates in cells in which Srp54 synthesis has been repressed under the control of a regulated promoter, indicating that S. pombe SRP functions in protein targeting [1].
• Deltaapm1 cells also showed the massive accumulation of the exocytic v-SNARE Syb1 in the Golgi/endosomes and a reduced secretion of acid phosphatase [2].
• Here we describe a mutant, sec8-1, that is defective in cell separation but not in other aspects of cytokinesis. sec8-1 mutants accumulate about 100-nm vesicles and have reduced secretion of acid phosphatase, suggesting that they are defective in exocytosis [3].
• Pho4 is not genetically linked to the phosphate repressible acid phosphatase gene pho1 [4].
• S. pombe is not unique in having a thiamin repressible acid phosphatase [4].

Biological context of SPBC4.06

• According to DNA and amino acid sequence data, the S. pombe acid phosphatase has a molecular weight of 50,600 [5].
• The Schizosaccharomyces pombe acid phosphatase structural gene (PHO 1) was isolated by complementation of an S. pombe acid phosphatase mutant with a wild type S. pombe DNA recombinant plasmid library [5].
• Phosphate and thiamin repressible acid phosphatase differ in their substrate specificity [4].
• Newly synthesised acid phosphatase was transported and secreted to the same extent and with the same kinetics whether or not the Golgi was unstacked [6].
• Synchronous cultures prepared by selection from an elutriating rotor were used to measure activity changes during the cell cycle of the following enzymes: acid phosphatase in Schizosaccharomyces pombe and Saccharomyces cerevisiae, alpha-glucosidase in S. cerevisiae and beta-galactosidase in Kluyveromyces lactis [7].

Anatomical context of SPBC4.06

• Furthermore, the over-expression of the Ryh1T25N mutant inhibited the acid phosphatase glycosylation and exacerbated the cell wall integrity of ypt3-i5 mutant, but had no effect on those of wild-type cells [8].
• Growth conditions determine how much of translated 54-kDa acid phosphatase is glycosylated to the 72-kDa form and how much remains unglycosylated in membranes [9].
• The 72-kDa form and the unglycosylated form of acid phosphatase are not secreted or transported to the plasma membrane [9].
• These mutational lesions apparently block transport of acid phosphatase from the endoplasmic reticulum to the Golgi apparatus [10].

Associations of SPBC4.06 with chemical compounds

• Identification and characterization of thiamin repressible acid phosphatase in yeast [4].
• Unlike ligand binding to mammalian calnexin, glucose trimming and reglucosylation of acid phosphatase by UDP-Glc:glycoprotein glucosyltransferase were shown to be dispensable for its binding to Cnx1p [11].
• However, Cnx1p stably associated with unglycosylated acid phosphatase after treatment with the core-glycosylation inhibitor tunicamycin [11].
• Schizosaccharomyces pombe acid phosphatase (APh) is a secreted cell surface glycoprotein which is deficient in pho1 mutants [12].
• Expression of Schizosaccharomyces pombe pho1-encoded acid phosphatase is transcriptionally regulated by adenine and phosphate [13].

Other interactions of SPBC4.06

• Disruption of gma12+ and gmh3+ also caused an increase in electrophoretic mobility of acid phosphatase, indicating their involvement in the galactosylation of cell surface glycoproteins [14].
• The nucleotide sequence of this gene is given here and it is shown that it matches the amino acid sequence of thiamin-repressible acid phosphatase, corroborating genetic evidence that pho4 represents the structural gene of this enzyme [15].

Analytical, diagnostic and therapeutic context of SPBC4.06

• At restrictive temperature the mutant cells accumulated the secretory protein acid phosphatase in a form that appeared to be fully glycosylated and acquired a population of vesicles detectable by electron microscopy [16].
• These two sequences map of different genetic loci and show no cross hybridization by Southern blotting. pSp4C/2 was found to contain the PHO1 gene, and cells transformed with this plasmid produce a protein which cross-reacts with antibodies raised against the protein moiety of APh [12].

References