Disease relevance of PFN1

• The complete amino acid sequence of Acanthamoeba profilin was determined by aligning tryptic, chymotryptic, thermolysin, and Staphylococcus aureus V8 protease peptides together with the partial NH2-terminal sequences of the tryptophan-cleavage products [1].
• It was recently reported that profilin is overexpressed in glomerular mesangial cells (MC) of rats with anti-Thy-1.1-induced glomerulonephritis and is accumulated in the extracellular space around MC [2].
• ADP-ribosylation of actin at Arg 177 by Clostridium perfringens iota toxin increased the nucleotide dissociation rate from 2.2 x 10(-3) s-1 to 4.5 x 10(-3) s-1 without affecting the profilin-induced stimulation of nucleotide exchange [3].
• Listeria monocytogenes intracellular migration: inhibition by profilin, vitamin D-binding protein and DNase I [4].
• Birch profilin was purified from pollen or as a recombinant protein from Escherichia coli, using poly(L-proline) affinity chromatography and a monoclonal antibody for the identification of the isolated product [5].

High impact information on PFN1

• Using affinity chromatography on either profilin isoform, we identified profilin II as the preferred ligand for VASP in bovine brain extracts [6].
• The complementary affinities of the profilin isoforms for PIP2 and the proline-rich peptides offer the cell an opportunity to direct actin assembly at different subcellular localizations through the same or different signal transduction pathways [6].
• The mammalian profilin isoforms display complementary affinities for PIP2 and proline-rich sequences [6].
• Our results indicate that profilin and profilactin can function as effective regulators for at least a subset of actin filaments in living cells [7].
• Previous studies have yielded conflicting results concerning the physiological role of profilin, a 12-15-kD actin- and phosphoinositide-binding protein, as a regulator of actin polymerization [7].

Biological context of PFN1

• The amino acid sequence of profilin from calf spleen [8].
• These results support a polymerization mechanism where the profilin-actin heterodimer binds to the (+)-end of actin filaments, followed by dissociation of profilin, and ATP hydrolysis and P(i) release from the actin subunit as it assumes its stable conformation in the helical filament [9].
• For a detailed analysis of the profilin-actin interaction, we designed several point mutations in bovine profilin I by computer modeling [10].
• These results suggest that extracellular profilin may be involved in the progression of glomerular diseases, by affecting cell growth [2].
• Effects of single amino acid substitutions in the actin-binding site on the biological activity of bovine profilin I [10].

Anatomical context of PFN1

• Profilin regulates the behavior of the eukaryotic microfilament system through its interaction with non-filamentous actin [11].
• However, the injection of profilin causes no detectable perturbation to the cell-substrate focal contact and no apparent depolymerization of filaments in either the nonlamellipodial circumferential band or the contractile ring of dividing cells [7].
• Profilin and beta/gamma-actin from calf thymus were covalently linked using the zero-length cross-linker 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide in combination with N-hydroxysuccinimide, yielding a single product with an apparent molecular mass of 60 kDa [9].
• These findings indicate that profilin in the extracellular space can bind to cell surface receptors of MC and act as an inducer of signal transduction [2].
• When microinjected into fibroblasts, F59A colocalized with the endogenous profilin and actin in ruffling areas, suggesting that profilins are targeted to and tethered at these sites by ligands other than actin [10].

Associations of PFN1 with chemical compounds

• These residues display a strained conformation in crystalline profilin-actin but may allow the formation of a hydrogen bond between the N-acetyl carbonyl group of profilin and the phenol hydroxyl group of Tyr188 in actin [11].
• Bovine profilin crystals (space group C2; a = 69.15 A, b = 34.59 A, c = 52.49 A; alpha = gamma = 90 degrees, beta = 92.56 degrees) were grown from a mixture of poly(ethylene glycol) 400 and ammonium sulfate [11].
• Acanthamoeba profilin contains 125 amino acid residues, is NH2-terminally blocked, and has trimethyllysine at position 103 [1].
• Finally it was shown that the two isoforms of actin can be separated from each other in the absence of profilin also by chromatography on hydroxyapatite [12].
• The two forms of profilin, PI (intact form) and PII (lacking the COOH-terminal glutamine and tyrosine residues) (Malm, B., Larsson, H., and Lindberg, U. (1983) J. Muscle Res. Cell Motil. 4, 569-588), were found unequally distributed between the two major peaks of PA, such that PA gamma contained mainly PI and PA beta both PI and PII [12].

Physical interactions of PFN1

• X-ray diffraction data were collected on an imaging plate scanner at the DORIS storage ring (DESY, Hamburg), and were phased by molecular replacement, using a search model derived from the 2.55 A structure of profilin complexed to beta-actin [11].
• Profilin II binds to poly(L-proline) more strongly than does profilin I; this is especially evident at more acidic pH values [13].
• Deletion of the proline-rich domain of VASP abolishes its ability to bind profilin but does not affect ruffling or stress fiber formation [14].

Other interactions of PFN1

• Moreover, the PIP2 phosphatase activity of native p150 purified from bovine brains is not inhibited by profilin, cofilin, or alpha-actinin, although PLCdelta1 activity is markedly inhibited by these proteins [15].
• We show further that PIP2 effectively competes for binding of profilin I to poly-L-proline, since this isoform, but not profilin II, can be eluted from a poly-L-proline column with PIP2 [6].
• Effects of profilin and thymosin beta4 on the critical concentration of actin demonstrated in vitro and in cell extracts with a novel direct assay [16].
• Effects of ADP-ribosylation of skeletal muscle alpha-actin by Clostridium perfringens iota toxin and by turkey erythrocyte ADP-ribosyltransferase A on profilin-regulated nucleotide exchange and ATPase activity were compared [3].
• This is confirmed by treatment of profilin (+Tyr) with carboxypeptidase A, which removes the C-terminal tyrosine (rapidly) and the penultimate glutamine residue (slowly), and thereby converts it to the other form as judged by chromatography on phosphocellulose [17].

Analytical, diagnostic and therapeutic context of PFN1

• Crystallization and structure determination of bovine profilin at 2.0 A resolution [11].
• The three-dimensional structure of bovine profilin-beta-actin has been solved to 2.55 A resolution by X-ray crystallography [18].
• Sequence analysis and x-ray crystallographic investigations showed that the cross-linked residues were glutamic acid 82 of profilin and lysine 113 of actin [9].
• The interaction of bovine spleen profilin with ATP- and ADP-G-actin and poly(L-proline) has been studied by spectrofluorimetry, analytical ultracentrifugation, and rapid kinetics in low ionic strength buffer [19].
• The effect on the structure of profilin of phosphatidylinositol 4,5-bisphosphate (PIP2) binding was probed by fluorescence and circular dichroism (CD) spectroscopy [20].

References