Gandhi, A. | bioRxiv Science

bioRxiv2020

Structural basis of the dynamic human CEACAM1 monomer-dimer equilibrium

Human (h) carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) function depends upon IgV-mediated homodimerization or heterodimerization with host ligands, including hCEACAM5 and hTIM-3, and a variety of microbial pathogens. However, there is little structural information available on how hCEACAM1 transitions between monomeric and dimeric states which in the latter case is critical for initiating hCEACAM1 activities. We therefore mutated residues within the hCEACAM1 IgV GFCC face including V39, I91, N97 and E99 and examined hCEACAM1 IgV monomer-homodimer exchange using differential scanning fluorimetry, multi-angle light scattering, X-ray crystallography and/or nuclear magnetic resonance. From these studies, we describe hCEACAM1 homodimeric, monomeric and transition states at atomic resolution and its conformational behavior in solution through NMR assignment of the wildtype (WT) hCEACAM1 IgV dimer and N97A monomer. These studies reveal the flexibility of the GFCC face and its important role in governing the formation of hCEACAM1 dimers and potentially heterodimers.

immunology↗

bioRxiv2020

JAK Inhibitors Suppress Colon Cancer Cachexia-Associated Anorexia and Adipose Wasting in Mice

BackgroundCachexia (CX), a syndrome of muscle atrophy, adipose loss, and anorexia, is associated with reduced survival in cancer patients. The colon adenocarcinoma C26c20 cell line secretes the cytokine leukemia inhibitor factor (LIF) which induces CX. We characterized how LIF promotes CX-associated weight loss and anorexia in mice through JAK-dependent changes in adipose and hypothalamic tissues. MethodsCX was induced in vivo with C26c20 colon adenocarcinoma cells or recombinant LIF administration in the absence or presence of JAK inhibitors. Blood, adipose, and hypothalamic tissues were collected and processed for cyto/adipokine ELISAs, immunoblot analysis, and quantitative RT-PCR. CX was induced in vitro by stimulating differentiated adipocytes with recombinant LIF or IL-6 in the absence or presence of lipase or JAK inhibitors. These activated adipocytes were processed for lipolysis, immunoblot analysis, and RT-PCR. ResultsTumor-secreted LIF induced changes in adipose tissue expression and serum levels of IL-6 and leptin in a JAK-dependent manner influencing CX-associated adipose wasting and anorexia. We identified two JAK inhibitors that block cytokine-mediated adipocyte lipolysis and IL-6 induction using an in vitro CX lipolysis assay. JAK inhibitors administered to in vivo colon cancer CX mouse models led to 1) a decrease in STAT3 phosphorylation in hypothalamic and adipose tissues, 2) a reverse in the CX serum cyto/adipokine signature, 3) a delay in colon cancer CX-associated anorexia and adipose loss, and 4) an improvement in overall survival. ConclusionsJAK inhibitors suppress cytokine-associated adipose loss and anorexia in multiple in vitro and in vivo models of cancer CX.

cancer biology↗