Sérine | EPFL Graph Search

La sérine (abréviations IUPAC-IUBMB : Ser et S) est un acide dont l'énantiomère L est l'un des aminés protéinogènes, encodé sur les ARN messagers par les codons UCU, UCC, UCA, UCG, AGU et AGC Description Structurellement semblable à l'alanine mais avec un groupe hydroxyle sur le , elle forme un résidu polaire avec une fonction alcool légèrement acide qui peut être phosphorylé en . Fonctions La sérine est l'un des acides aminés les plus abondants dans les protéines. La D-Sérine, synthétisée par la sérine racémase à partir de L-serine, sert de signal neuronal en activant le récepteur NMDA dans le cerveau. Il a été récemment montré que dans un milieu de culture minimum, supplémenté avec du sérum dialysé au lieu de sérum entier, la culture d'une grande variété de souches de cellules humaines est possible, mais que la croissance régulière ou optimale d'un certain nombre de ces cellules (HeLa, HeLa S3, conjonctivale, ou KB) est inhibée, en raison semble-t-il d'

Novel compartment-specific biosensors reveal a complementary subcellular distribution of bioactive Furin and PC7

Pierpaolo Ginefra

Proprotein Convertases (PCs) constitute a family of serine proteases that activate various hormones, growth factors and cell adhesion molecules by mediating endoproteolytic cleavage of their secreted inactive precursors during their transit in the secretory pathway. Their physiological roles in most tissues, in cancer and other diseases have remained nowadays poorly defined, partly because of technical hurdles in clearly distinguishing functionally overlapping PC activities from each other. Related to this, a major unsolved question is where, among the different subcellular compartments of the secretory pathway, substrate cleavage takes place. To address these questions, we mapped intracellular PC activities of two unrelated cell lines (HEK293T and B16F1 melanoma) by ratiometric and Förster Resonance Energy Transfer (FRET)-based imaging of the PC-specific biosensors, called cell-linked indicator of proteolysis (CLIP)v3 and CLIPv4 respectively, which are sorted to different subcellular compartments by specific trafficking signals. Until now, PCs have been thought to cleave the majority of the substrates in the trans-Golgi network (TGN). By contrast, our analysis of compartment-specific CLIPv3 and CLIPv4 variants in cultured cells suggested that PC activities are much higher in post-exocytic compartments. Furthermore, imaging in B16F1 Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-edited clones for endogenously expressed Furin or PC7, revealed an enrichment of Furin activity in endosomes compared to TGN, whereas PC7 activity was confined to a distinct compartment resistant to the pan-PC inhibitor CMK, demonstrating that endogenous Furin and PC7 are biologically active in distinct compartments. In addition, we also demonstrated that substrate and protease localization are rate-limiting of how efficiently a given substrate is processed. PC inhibition represses human primary melanoma cells motility and migration in vitro and proliferation in other skin cancer cells both in vitro and in vivo. To elucidate the roles of PC activities in melanoma progression and differentiation, we evaluated relative contribution of Furin and PC7 in B16F1 tumor grafts. Both proteins were required for tumor pigmentation, whereas Furin deletion reduced tumor growth, but its loss may be rescued by PC7 deletion. Altogether, these findings will be important to inform future therapeutic approaches and strategies for targeting PCs to preferentially block oncogenic activities.

EPFL2018

Neutron Reflectivity Study on the Postpolymerization Modification of Poly(2-hydroxyethyl methacrylate) Brushes

Juan Pablo Hinestrosa Salazar, Harm-Anton Klok

Postpolymerization modification reactions are widely employed to prepare functional polymer brushes. Relatively little is known, however, about the distribution of functional groups in such postmodified brushes. Using neutron reflectometry and UV-vis spectroscopy as principal tools, this article investigates the p-nitrophenyl chloroformate (NPC)-mediated postpolymerization modification of poly(2-hydroxyethyl methacrylate) (PHEMA) brushes, prepared via surface-initiated atom transfer radical polymerization, with D-10 leucine and D-3 serine. The neutron reflectometry experiments indicate that the postpolymerization modification depends both on brush thickness and grafting density. Whereas for dense brushes, postpolymerization modification with D-10 leucine is limited to the top similar to 200 angstrom of the brush, independently of the brush thickness, the extent of postmodification can be significantly enhanced by decreasing the grafting density of the brush or by using the more hydrophilic and sterically less demanding D-3 serine, which reflects the ability of this amino acid to more readily penetrate the brush. UV-vis experiments revealed that the NPC activation is also nonuniform, but brush thickness and grafting density dependent, which adds to brush thickness and density and the nature of the amino acid as another of a complex set of variables that determine the final distribution of functional groups in postmodified brushes.

American Chemical Society2011

Synthesis of a C-linked disaccharide analogue of the Thomsen Friedenreich (TF)-epitope a-O-conjugated to L-serine and formation of a cluster as potential anticancer vaccine

Loay Awad

Cell surface glycoproteins and glycolipids are responsible for cellular recognition processes. Vaccination is the procedure whereby the immune system is induced to create antibodies against a foreign molecule involved in disease or viral infection. In many disease states, the oligosaccharide chains presented on cell surface glycoprotein are altered. In some tumors, the glycan chains of glycoproteins are attenuated to only a few sugar residues. In the case of the TF-antigen, the polysaccharide chains have been shortened to a galactose-β-(1–>3)-N-acetyl-galactosamine disaccharide structure α-linked to a serine or threonine. Immunogenicity of this epitope in synthetic vaccines has been demonstrated. However, this disaccharide conjugate is relatively short-lived in the blood stream because of its hydrolysis catalysed by ubiquitous glycosidases in vivo. C-disaccharides are sugar mimetics whose interglycosidic linkage is non-hydrolysable as required for a disaccharide-based vaccine. In the first part of the work, we report the first synthesis of TF-antigen analogues applying the methodology developed by our group for the synthesis of C(1–>3)-disaccharides. Conjugate addition of diethylaluminium iodide (Et2AlI) to isolevoglucosenone leads to an aluminium enolate, which reacts with the sugar derived carbaldehyde, 2,6-anhydro-3,4,5,7-tetrakis-O-[(tert-butyldimethyl)silyl]-D-glycero-L-manno-heptose, to give an aldol. The convergent and stereoselective synthesis of this adduct allows us to obtain C(1–>3)-disaccharides. Reduction of the moiety derived from isolevoglucosenone with lithium borohydride, followed by cleavage of the 1,6-anhydro bridge produces C-disaccharides with D-galacto configuration. Königs-Knorr glycosidation of N-Fmoc-serine tert-butylester, followed by reduction of azide moiety to the corresponding acetamido group allows us to obtain TF-antigen analogues linked either by hydroxymethano (-CH(OH)-) or methano (-CH2-) group. In a second part we report the synthesis of a fully deprotected thio-glycotripeptide based on the TFantigen -C-analogues linked by hydroxymethano - N-acetyl-O-{α-D-glyco}-D-seryl-O-{α-D-glyco}-D-seryl-rac-N-(3-[(acetylthio)amino]propyl)-O-{α-D-glyco}-D-serinamide, which was covalently conjugated to the KLH protein carrier via Michael addition reaction. Biological trials with the TF (analogues)-KLH are in progress. We report also the synthesis of fully deprotected TF-antigen -C-analogues linked by hydroxymethano (-CH(OH) and methano (-CH2-) group. their conformational analysis is currently in progress.