ABSTRACT
Elimination of autoreactive developing B cells is an important mechanism to prevent autoantibody production. However, how B cell receptor (BCR) signaling triggers apoptosis of immature B cells remains poorly understood. We show that BCR stimulation up-regulates the expression of the lysosomal-associated transmembrane protein 5 (LAPTM5), which in turn triggers apoptosis of immature B cells through two pathways. LAPTM5 causes BCR internalization, resulting in decreased phosphorylation of SYK and ERK. In addition, LAPTM5 targets the E3 ubiquitin ligase WWP2 for lysosomal degradation, resulting in the accumulation of its substrate PTEN. Elevated PTEN levels suppress AKT phosphorylation, leading to increased FOXO1 expression and up-regulation of the cell cycle inhibitor p27Kip1 and the proapoptotic molecule BIM. In vivo, LAPTM5 is involved in the elimination of autoreactive B cells and its deficiency exacerbates autoantibody production. Our results reveal a previously unidentified mechanism that contributes to immature B cell apoptosis and B cell tolerance.
Subject(s)
Apoptosis , Immune Tolerance , Membrane Proteins , Precursor Cells, B-Lymphoid , Cyclin-Dependent Kinase Inhibitor p27/metabolism , Forkhead Box Protein O1/metabolism , Humans , Lysosomes/metabolism , Membrane Proteins/genetics , PTEN Phosphohydrolase/metabolism , Precursor Cells, B-Lymphoid/metabolism , Proto-Oncogene Proteins c-akt/metabolism , Ubiquitin-Protein Ligases/metabolismABSTRACT
We present the finding of a dimeric ACE2 peptide mimetic designed through side chain cross-linking and covalent dimerization. It has a binding affinity of 16 nM for the SARS-CoV-2 spike RBD, and effectively inhibits the SARS-CoV-2 pseudovirus in Huh7-hACE2 cells with an IC50 of 190 nM and neutralizes the authentic SARS-CoV-2 in Caco2 cells with an IC50 of 2.4 µM. Our study should provide a new insight for the optimization of peptide-based anti-SARS-CoV-2 inhibitors.
Subject(s)
Antiviral Agents/pharmacology , Peptide Fragments/pharmacology , Peptidomimetics/pharmacology , SARS-CoV-2/drug effects , Amino Acid Sequence , Angiotensin-Converting Enzyme 2/chemistry , Antiviral Agents/chemical synthesis , Antiviral Agents/metabolism , Cell Line, Tumor , Humans , Microbial Sensitivity Tests , Peptide Fragments/chemical synthesis , Peptide Fragments/metabolism , Peptidomimetics/chemical synthesis , Peptidomimetics/metabolism , Protein Binding , Protein Domains , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/metabolismABSTRACT
A series of cyclic Arg-rich mitochondria-penetrating peptides were prepared with variation in the macrocycle size and the chirality of Arg residues. A cyclic heptapeptide was demonstrated to be an efficient mitochondria-specific delivery vector for delivering membrane impermeable peptides.
Subject(s)
Cell Membrane/metabolism , Cell-Penetrating Peptides/metabolism , Mitochondria/metabolism , Cell Membrane/chemistry , Cell Survival , Cell-Penetrating Peptides/chemistry , Cyclization , HeLa Cells , Humans , Mitochondria/chemistry , Molecular ConformationABSTRACT
A new robust strategy was reported for the epimerization-free synthesis of C-terminal Cys-containing peptide acids through mercaptoethanol-mediated hydrolysis of peptide thioesters prepared in situ from peptide hydrazides. This simple-to-operate and highly efficient method avoids the use of derivatization reagents for resin modification, thus providing a practical avenue for the preparation of C-terminal Cys-containing peptide acids.
