Biology subjects

Alexander-Brett, J.

Publications and source records attributed to Alexander-Brett, J..

3 recordsLinked to original sources

bioRxiv2025

HSP70 is a chaperone for IL-33 secretion and function in chronic airway disease

IL-33 is a key driver of type 2 inflammation relevant to airway epithelial biology. However, the mechanisms for IL-33 secretion and regulation in the context of chronic airway disease is poorly understood. Here we report a disease-associated isoform IL-33{Delta}34 that escapes nuclear sequestration to be tonically secreted by recruitment to unconventional protein secretory pathways by HSP70. IL-33{Delta}34 interacts with HSP70 within cells to be targeted to secretory organelles through coordinated binding to phosphatidylserine (PS). Once secreted, this HSP70/cytokine complex stabilizes IL-33{Delta}34 by inhibiting oxidation/degradation thereby enhancing IL-33{Delta}34-receptor binding and activity. We find evidence for IL-33, HSP70 and chaperonin TCP-1 are dysregulated in human chronic airway disease. This phenomenon is reflected in differential proteomics of diseased bronchial wash extracellular vesicles. This study confirms proteostasis intermediates, chiefly HSP70, as a chaperone for non-canonical IL-33{Delta}34 secretion and activity that may be amenable for therapeutic targeting in airway diseases such as asthma and COPD. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/635799v2_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@b01ea9org.highwire.dtl.DTLVardef@ad18c9org.highwire.dtl.DTLVardef@364c0forg.highwire.dtl.DTLVardef@bba135_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2024

Biophysical mapping of TREM2-ligand interactions reveals shared surfaces for engagement of multiple AD ligands

TREM2 is a signaling receptor expressed on microglia that has emerged as an important potential drug target for Alzheimers disease and other neurodegenerative diseases. While a number of TREM2 signaling ligands have been identified, little is known regarding the structural details of how it engages them. To better understand this, we created a protein library of 28 different TREM2 variants and 11 different sTREM2 variants that could be used to map interactions with various ligands using biolayer interferometry (BLI). The variants are located in previously identified putative binding surfaces on TREM2 called the hydrophobic site, basic site, and site 2. We found that mutations to the hydrophobic site ablated binding to apoE4, oAb42, and TDP-43. Competition binding experiments further supported that apoE4 and oAb42 share overlapping binding sites on TREM2. In contrast, binding to IL-34 was mediated by the basic site at a surface centering on R76. Competition binding experiments validated a unique site for IL-34, showing little to no competition with either oAb42 or apoE4. Altogether, our results suggest that TREM2 utilizes the hydrophobic site (consisting of CDR1, CDR2, and CDR3) as a common site to engage multiple ligands, and further implies that pharmaceutical strategies targeting this surface might be effective to modulate TREM2 functions.

biophysics↗

bioRxiv2024

Structural and functional analysis of TREM2 interactions with amyloid beta reveal molecular mechanisms that mediate phagocytosis of oligomeric amyloid beta

The TREM2 receptor is expressed on microglia in the brain, where it plays critical roles regulating microglia function. TREM2 engages a number of ligands involved in Alzheimers disease, and consequent signaling triggers phagocytosis, activation, survival, and proliferation. TREM2 has emerged as a drug target for AD, however very little is known regarding the structural basis for TREM2 microglial functions. Here we investigated the engagement of oligomeric amyloid beta (oA{beta}42) with TREM2. Using familial variants of amyloid beta, we show that mutations in the N-terminal portion of A{beta}, notably residues H6 and D7, disrupt binding to TREM2. We then co-crystallized TREM2 with A{beta}(1-8) peptide and determined the high resolution crystal structure. The structure revealed the peptide binds to the hydrophobic site of TREM2, closest to CDR1. Mutational and binding studies using BLI confirmed that mutations to the hydrophobic site ablate binding to oA{beta}42. Finally, we show that these interactions are critical to triggering phagocytosis of oA{beta}42, as oA{beta}42 variants H6R and D7N are not phagocytosed. Altogether, these data indicate that TREM2 engages oA{beta}42 using the hydrophobic site on TREM2 and the N-terminal portion of A{beta}, and that this interaction is critical to trigger signaling and phagocytosis.

biophysics↗