La métamorphose de l’amour dans L’Éthique de Spinoza

Spinoza’s Ethics has a robust and underappreciated theory of love. In this paper, I show that Spinoza’s discussion of love, which stands at a crossroads between his ethics and his epistemology, details the metamorphosis of love in the philosopher’s mind – from passionate love to intellectual love of God, and from imagination or opinion to scientia intuitiva. This metamorphosis is responsible for the closely interrelated philosopher’s morality and the perfection of their understanding, which are closely linked. Reading Spinoza’s guide to ethical and philosophical progress through the prism of his theory of love holds the key to understanding some of the most perplexing issues presented in the second half of Part 5, namely, the nature of the intellectual love of God and the object of the third kind of knowledge.Spinozina Etika ima robusnu i podcijenjenu teoriju ljubavi. U ovom članku pokazujem da Spinozina rasprava o ljubavi, smještena na križištu između njegove etike i njegove epistemologije, opisuje metamorfozu ljubavi u filozofovu umu – od strastvene ljubavi do intelektualne ljubavi prema Bogu, te od imaginacije ili mnijenja do scientia intuitiva. Metamorfoza je odgovorna za međusobno usko povezanu filozofovu moralnost i usavršenje razumijevanja. Čitati Spinozine upute za etički i filozofijski napredak kroz prizmu njegove teorije o ljubavi sadrži ključ za razumijevanje nekih od najviše zbunjujućih problema predočenih u drugoj polovici Petog dijela, točnije, prirode intelektualne ljubavi za Bogom i predmeta treće vrste znanja.Spinozas Ethik hat eine robuste und unterschätzte Theorie der Liebe. In diesem Paper zeige ich, dass Spinozas Erörterung der Liebe, die am Scheideweg zwischen seiner Ethik und seiner Epistemologie steht, die Metamorphose der Liebe im Geist des Philosophen detailliert schildert – von leidenschaftlicher Liebe zu intellektueller Liebe zu Gott wie auch von Vorstellungskraft oder Meinung zur Scientia intuitiva. Diese Metamorphose ist verantwortlich für die eng zusammenhängende Moralität des Philosophen und die Vervollkommnung des Verständnisses, die eng miteinander verknüpft sind. Die Lektüre von Spinozas Leitfaden zum ethischen und philosophischen Fortschritt durch das Prisma seiner Liebestheorie enthält den Schlüssel zum Verständnis einiger der verwirrendsten Probleme, die in der zweiten Hälfte des Fünften Teils präsentiert werden, nämlich der Natur der intellektuellen Liebe zu Gott sowie des Gegenstands der dritten Gattung des Wissens.L’Éthique de Spinoza a une théorie de l’amour robuste et sous-valorisée. Dans cet article, je montre que le débat de Spinoza sur l’amour, qui se situe au croisement entre son éthique et son épistémologie, décrit la métamorphose de l’amour dans l’esprit du philosophe – de l’amour passionnel à l’amour intellectuel envers Dieu, et de l’imagination et l’opinion à la scientia intuitiva. Cette métamorphose est responsable de la moralité du philosophe intimement liée à la perfection de sa compréhension. La lecture des conseils de Spinoza, en vue d’un progrès éthique et philosophique à travers le prisme de sa théorie de l’amour, contient la clé pour comprendre certains des problèmes les plus déroutants présentés dans la deuxième moitié de la Cinquième partie, plus précisément, la nature de l’amour intellectuel de Dieu et le sujet du troisième genre de connaissance

Specific Recognition of p53 Tetramers by Peptides Derived from p53 Interacting Proteins

Oligomerization plays a major role in regulating the activity of many proteins, and in modulating their interactions. p53 is a homotetrameric transcription factor that has a pivotal role in tumor suppression. Its tetramerization domain is contained within its C-terminal domain, which is a site for numerous protein-protein interactions. Those can either depend on or regulate p53 oligomerization. Here we screened an array of peptides derived from proteins known to bind the tetrameric p53 C-terminal domain (p53CTD) and identified ten binding peptides. We quantitatively characterized their binding to p53CTD using fluorescence anisotropy. The peptides bound tetrameric p53CTD with micromolar affinities. Despite the high charge of the binding peptides, electrostatics contributed only mildly to the interactions. NMR studies indicated that the peptides bound p53CTD at defined sites. The most significant chemical shift deviations were observed for the peptides WS100B(81–92), which bound directly to the p53 tetramerization domain, and PKCα(281–295), which stabilized p53CTD in circular dichroism thermal denaturation studies. Using analytical ultracentrifugation, we found that several of the peptides bound preferentially to p53 tetramers. Our results indicate that the protein-protein interactions of p53 are dependent on the oligomerization state of p53. We conclude that peptides may be used to regulate the oligomerization of p53

Agonist-induced dimer dissociation as a macromolecular step in G protein-coupled receptor signaling

G protein-coupled receptors (GPCRs) constitute the largest family of cell surface receptors. They can exist and act as dimers, but the requirement of dimers for agonist-induced signal initiation and structural dynamics remains largely unknown. Frizzled 6 (FZD6) is a member of Class F GPCRs, which bind WNT proteins to initiate signaling. Here, we show that FZD6 dimerizes and that the dimer interface of FZD6 is formed by the transmembrane a-helices four and five. Most importantly, we present the agonist-induced dissociation/re-association of a GPCR dimer through the use of live cell imaging techniques. Further analysis of a dimerization-impaired FZD6 mutant indicates that dimer dissociation is an integral part of FZD6 signaling to extracellular signal-regulated kinases1/2. The discovery of agonistdependent dynamics of dimers as an intrinsic process of receptor activation extends our understanding of Class F and other dimerizing GPCRs, offering novel targets for dimerinterfering small molecules

Thermal denaturation curves of p53CTD L344A in the presence of peptides from the array.

<p>20 µM protein was heated from 25°C to 65°C with or without 100 µM peptide. The data were fit to a sigmoidal curve describing a transition between two states. Raw data for two repeats (squares and hollow circles) are shown in the background. The dashed lines represent the averaged melting temperatures for both repeats.</p

Ionic strength-dependent binding of the peptides to p53CTD.

<p>ln(<i>K</i>_d) is plotted vs. ln(NaCl activity) for the tightest binding peptides. The data were fit to a linear model.</p

Binding sites for p53CTD on two PKCα domains.

<p>A) The C2 domain of PKCα (pdb 1dsy). Residues 271–292 are colored in red. B) The catalytic domain of PKCα (pdb 3iw4). Residues 641–655 are colored in red.</p

Screening of the peptide array for binding to p53CTD and the constructs p53Tet and p53NRD.

<p>Peptides that interacted with p53NRD (p53 361–393) are marked in green. The peptide WS100B(81–92) that interacted with p53Tet is marked in yellow. The peptide PKCα(281–295) that bound more tightly to full-length p53CTD than to p53NRD is marked in red.</p

Changes in chemical shifts of ¹⁵N-labeled p53CTD upon incubation with various peptides.

<p>¹⁵N–¹H HSQC NMR spectra of the protein were measured with and without peptide, and the changes in chemical shifts were calculated as (δΔ¹H²+(δΔ¹⁵N/5)²)⁰.⁵. The left panel shows the chemical shift deviations for backbone amide nitrogen atoms, and the right panel shows the chemical shift deviations for side chain nitrogen atoms. Numbers on the x-axis are arbitrary serial numbers for peaks and are unrelated to residue sequence.</p

Sedimentation profiles of FlAsH-labeled p53 (25–50 nM) measured in the presence of the peptides.

<p>A) PKCα(271–285) had no significant effect on the profile. B) Peptides that shifted the tetramer peak. C) Concentration dependent behavior of the peptides. Sedimentation profiles were measured with different concentrations of WS100B(61–75). Similar behavior was observed for the other peptides in B (data not shown). D) Behavior of Cul7(376–390). This peptide binds p53 only weakly, and causes a shift of the tetramer peak at very high peptide concentrations. Similar behavior was observed for PARC(386–400).</p