Disease relevance of PFY1

• Vaccinia profilin binds to phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 4-monophosphate in micelles and large unilamellar vesicles, but not to phosphatidylserine or phosphatidylcholine [1].
• We expressed in Escherichia coli the vaccinia virus gene for a protein similar to vertebrate profilins, purified the recombinant viral profilin, and characterized its interactions with actin and polyphosphoinositides [1].

High impact information on PFY1

• We show that these diverse formins have the same basic properties: movement is processive in the absence or presence of profilin; profilin accelerates elongation; and actin ATP hydrolysis is not required for processivity [2].
• We propose that CAP and profilin provide a link between growth signals and remodeling of the cellular cytoskeleton [3].
• The phenotype of cells lacking PFY resembles that of cells lacking the CAP C-terminal domain [3].
• Thus, formin and profilin mediate actin nucleation by an Arp2/3-independent mechanism [4].
• However, fluid phase endocytosis is defective in act1-159 strains. act1-159 is synthetically lethal with cofilin and profilin mutants, supporting the conclusion that mutations in all of these genes impair the polymerization/ depolymerization cycle [5].

Chemical compound and disease context of PFY1

• Consequently, vaccinia profilin is more likely to influence phosphoinositide metabolism than actin assembly [1].

Biological context of PFY1

• The PFY1 promoter dispenses with classical transactivators and a consensus TATA box; however, it contains a canonic site for the abundant multifunctional nuclear factor rDNA enhancer-binding protein (Reb1p) combined with a dA.dT element [6].
• In contrast, overexpression of the profilin gene, PFY1, encoding an actin-binding protein, leads to no very obvious phenotype [7].
• In contrast, the patterns for profilin and the SH3 domain proteins suggest a shared binding site and commonality in mechanism [8].
• The severity of various morphological abnormalities of the strains was also attenuated with increased protein levels, suggesting that profilin polyproline-binding mutations are deleterious to cell growth unless overexpressed [9].
• In light of recent studies with profilins, we propose that Cdc3-profilin plays an essential role in cytokinesis by catalyzing the formation of the F-actin contractile ring [10].

Anatomical context of PFY1

• The yeast profilin gene (PFY1), encoding a housekeeping component of the actin cytoskeleton, is constitutively transcribed at a moderate level [6].
• Immunoblot analysis showed that profilin was localized in both the plasma membrane and cytosolic fractions of the cell [11].
• Profilin translocated back to the membrane fraction from the cytosol under growth conditions where plasma membrane levels of phosphatidylinositol 4,5-bisphosphate were replenished [11].
• Profilin plays an important role in actin organization in all eukaryotic cells through mechanisms that are still poorly understood [12].
• We had previously shown that Mid2p, a transmembrane protein and a potential cell wall sensor, is an effective multicopy suppressor of the profilin-deficient phenotype in Saccharomyces cerevisiae [12].

Associations of PFY1 with chemical compounds

• Replacement of the wild-type yeast profilin gene (PFY1) with a mutated form (pfy1-111) that has codon 72 changed to encode glutamate rather than arginine results in defects similar to, but less severe than, those that result from complete deletion of the profilin gene [13].
• Profilin may also link signaling pathways to actin cytoskeleton organization by binding to the phosphoinositide PIP(2) and to polyproline stretches on several proteins [14].
• The presence of phosphatidylinositol 4,5-bisphosphate in phospholipid vesicles was required for maximum profilin binding [11].
• These results suggested that phosphoinositide metabolism played a role in the localization of profilin [11].
• The subcellular localization of profilin was examined in vivo under growth conditions (i.e. inositol starvation of ino1 cells and glucose starvation of respiratory deficient cells) where plasma membrane levels of phosphatidylinositol 4,5-bisphosphate were depleted [11].

Physical interactions of PFY1

• Moreover, yeast two-hybrid and biochemical studies demonstrate that Bni1p and Bnr1p interact directly with profilin at the FH1 domains [15].
• Actin was bound to the profilin localized in the cytosol [11].
• All of the sec3 alleles genetically interact with a profilin mutation, pfy1-111 [16].

Enzymatic interactions of PFY1

• In vivo importance of actin nucleotide exchange catalyzed by profilin [14].

Regulatory relationships of PFY1

• Bni1p and Bnr1p: downstream targets of the Rho family small G-proteins which interact with profilin and regulate actin cytoskeleton in Saccharomyces cerevisiae [15].
• Overexpression of MID2 suppresses the profilin-deficient phenotype of yeast cells [17].

Other interactions of PFY1

• These results indicate that Bni1p and Bnr1p are potential targets of the Rho family members, interact with profilin and regulate the reorganization of actin cytoskeleton [15].
• These results indicate that Bnr1p directly interacts with Hof1p as well as with profilin to regulate cytoskeletal functions in S. cerevisiae [18].
• SEC3 mutations are synthetically lethal with profilin mutations and cause defects in diploid-specific bud-site selection [13].
• It contains the transcription termination region of the convergently transcribed yeast genes, GCY1 and PFY1, together with sequences corresponding to the mapped 3'-ends of the respective mRNAs [19].
• These phenotypes are similar to those of the mutant of PFY1, which encodes profilin, an actin-binding protein [15].

Analytical, diagnostic and therapeutic context of PFY1

• We are investigating structure-function relationships in profilin and actin by site-specific mutagenesis using a yeast, Saccharomyces cerevisiae, expression system to produce wild-type and mutant proteins [20].
• The structure of profilin from the budding yeast Saccharomyces cerevisiae has been determined by X-ray crystallography at 2.3 A resolution [21].
• The recombinant protein, isolated by affinity chromatography on poly(L-proline)-Sepharose followed by ion exchange chromatography, associates with non-muscle actin and phosphatidylinositol-(4,5)-bisphosphate as authentic profilin [22].

References