Pharmacological rescue of tumor intrinsic STING expression and immune response in LKB1-mutant lung cancer via the IAP-JAK regulatory axis

Harnessing the power of the immune system to treat cancer has become a core clinical approach. However, rewiring of intrinsic circuitry enables tumor cells to escape immune attacks, leading to therapeutic failure. Pharmacological strategies to reverse tumor genotype-dictated therapeutic resistance are urgently needed to advance precision immunotherapy. Here, we identify antagonists of Inhibitor of Apoptosis Protein (IAP) as potent sensitizers that restore immune-dependent killing of LKB1-mutant lung cancer cells. Mechanistic studies reveal an LKB1-IAP-JAK trimolecular complex that bridges the LKB1-mutant genotype with IAP-dependency and a STING-deficiency-mediated immune resistance phenotype. Ultimately, inhibition of IAP re-establishes JAK-regulated STING expression and DNA sensing pathway as well as enhanced cytotoxic immune cell infiltration and selective immune-dependent anti-tumor activity in an LKB1-mutant immune-competent mouse model. Thus, IAP-JAK-modulatory strategies, like IAP inhibitors, offer promising immunotherapy adjuvants to re-establish the responsiveness of "immunologically-cold" LKB1-mutant tumors to immune checkpoint inhibitors or STING-directed therapies.

Deletion of the Thrombin Proteolytic Site in Neurofascin 155 Causes Disruption of Nodal and Paranodal Organization

In the central nervous system, myelin is attached to the axon in the paranodal region by a trimolecular complex of Neurofascin155 (NF155) in the myelin membrane, interacting with Caspr1 and Contactin1 on the axolemma. Alternative splicing of a single Neurofascin transcript generates several different Neurofascins expressed by several cell types, but NF155, which is expressed by oligodendrocytes, contains a domain in the third fibronectinIII-like region of the molecule that is unique. The immunoglobulin 5–6 domain of NF155 is essential for binding to Contactin1, but less is known about the functions of the NF155-unique third fibronectinIII-like domain. Mutations and autoantibodies to this region are associated with several neurodevelopmental and demyelinating nervous system disorders. Here we used Crispr-Cas9 gene editing to delete a 9 bp sequence of NF155 in this unique domain, which has recently been identified as a thrombin binding site and implicated in plasticity of the myelin sheath. This small deletion results in dysmyelination, eversion of paranodal loops of myelin, substantial enlargement of the nodal gap, a complete loss of paranodal septate junctions, and mislocalization of Caspr1 and nodal sodium channels. The animals exhibit tremor and ataxia, and biochemical and mass spectrometric analysis indicates that while NF155 is transcribed and spliced normally, the NF155 protein is subsequently degraded, resulting in loss of the full length 155 kDa native protein. These findings reveal that this 9 bp region of NF155 in its unique third fibronectinIII-like domain is essential for stability of the protein.

A Journey to the Conformational Analysis of T-Cell Epitope Peptides Involved in Multiple Sclerosis

Multiple sclerosis (MS) is a serious central nervous system (CNS) disease responsible for disability problems and deterioration of the quality of life. Several approaches have been applied to medications entering the market to treat this disease. However, no effective therapy currently exists, and the available drugs simply ameliorate the destructive disability effects of the disease. In this review article, we report on the efforts that have been conducted towards establishing the conformational properties of wild-type myelin basic protein (MBP), myelin proteolipid protein (PLP), myelin oligodendrocyte glycoprotein (MOG) epitopes or altered peptide ligands (ALPs). These efforts have led to the aim of discovering some non-peptide mimetics possessing considerable activity against the disease. These efforts have contributed also to unveiling the molecular basis of the molecular interactions implicated in the trimolecular complex, T-cell receptor (TCR)–peptide–major histocompatibility complex (MHC) or human leucocyte antigen (HLA).

Crystal structure of the giant panda MHC class I complex: first insights into the viral peptide presentation profile in the bear family

ABSTRACTThe viral cytotoxic T lymphocyte (CTL) epitope peptides presented by classical MHC-I molecules require the assembly of a peptide-MHC-I-β2m (aka pMHC-I) trimolecular complex for TCR recognition, which is the critical activation link for triggering antiviral T cell immunity. Ursidae includes 5 genera and 8 species; however, research on T cell immunology in this family, especially structural immunology, is lacking. In this study, the structure of the key trimolecular complex pMHC-1 (aka pAime-128), which binds a peptide from canine distemper virus, was solved for the first time using giant panda as a representative species of Ursidae. The structural characteristics of the giant panda pMHC-I complex, including the unique pockets in the peptide-binding groove (PBG), were analyzed in detail. Comparing the panda pMHC-I to others in the bear family and extending the comparison to other mammals revealed distinct features. The interaction between MHC-I and β2m, the features of pAime-128 involved in TCR docking and CD8 binding, the anchor sites in the PBG, and the CTL epitopes of potential viruses that infect pandas were concretely clarified. Unique features of pMHC-I viral antigen presentation in the panda were revealed by solving the three-dimensional structure of pAime-128. The distinct characteristics of pAime-128 indicate an unusual event that emerged during the evolution of the MHC system in the bear family. These results provide a new platform for research on panda CTL immunity and the design of vaccines for application in the bear family.IMPORTANCEUrsidae includes 5 genera and 8 species; however, the study of its immunology, especially structural immunology, is extremely rare to date. In this paper, we first crystallized the key complex pMHC-I, taking the giant panda as its representative species. Structural characteristics of the giant panda pMHC-I complexes, contains the unique pockets of PBG were analyzed in detail. Comparison of the panda pMHC-I in the bear family and other mammals, almost definite features was displayed. Meanwhile, the interaction between HC and LV, the unique features of pMHC-I in the CD8 binding and TCR docking, validation of anchor site in the PBG, and epitopes of potential viruses infected with the pandas, were concretely clarified. These unique characteristics of pMHC-I clearly indicate an unusual situation during the evolution of MHC molecules in the endangered pandas. These results also provide a novel platform for further study of panda T cell immunology and vaccines.