SHEP1 partners with CasL to promote marginal zone B-cell maturation

Non-Muscle Myosin II A: Friend or Foe in Cancer?

Non-muscle myosin IIA (NM IIA) is a motor protein that belongs to the myosin II family. The myosin heavy chain 9 (MYH9) gene encodes the heavy chain of NM IIA. NM IIA is a hexamer and contains three pairs of peptides, which include the dimer of heavy chains, essential light chains, and regulatory light chains. NM IIA is a part of the actomyosin complex that generates mechanical force and tension to carry out essential cellular functions, including adhesion, cytokinesis, migration, and the maintenance of cell shape and polarity. These functions are regulated via light and heavy chain phosphorylation at different amino acid residues. Apart from physiological functions, NM IIA is also linked to the development of cancer and genetic and neurological disorders. MYH9 gene mutations result in the development of several autosomal dominant disorders, such as May-Hegglin anomaly (MHA) and Epstein syndrome (EPS). Multiple studies have reported NM IIA as a tumor suppressor in melanoma and head and neck squamous cell carcinoma; however, studies also indicate that NM IIA is a critical player in promoting tumorigenesis, chemoradiotherapy resistance, and stemness. The ROCK-NM IIA pathway regulates cellular movement and shape via the control of cytoskeletal dynamics. In addition, the ROCK-NM IIA pathway is dysregulated in various solid tumors and leukemia. Currently, there are very few compounds targeting NM IIA, and most of these compounds are still being studied in preclinical models. This review provides comprehensive evidence highlighting the dual role of NM IIA in multiple cancer types and summarizes the signaling networks involved in tumorigenesis. Furthermore, we also discuss the role of NM IIA as a potential therapeutic target with a focus on the ROCK-NM IIA pathway.

IGF1R signalling is a guardian of self-tolerance restricting autoantibody production

OBJECTIVE

Insulin-like growth factor 1 receptor (IGF1R) acts at the crossroad between immunity and cancer, being an attractive therapeutic target in these areas. IGF1R is broadly expressed by antigen-presenting cells (APC). Using mice immunised with the methylated albumin from bovine serum (BSA-immunised mice) and human CD14+ APCs, we investigated the role that IGF1R plays during adaptive immune responses.

METHODS

The mBSA-immunised mice were treated with synthetic inhibitor NT157 or short hairpin RNA to inhibit IGF1R signalling, and spleens were analysed by immunohistology and flow cytometry. The levels of autoantibody and cytokine production were measured by microarray or conventional ELISA. The transcriptional profile of CD14+ cells from blood of 55 patients with rheumatoid arthritis (RA) was analysed with RNA-sequencing.

RESULTS

Inhibition of IGF1R resulted in perifollicular infiltration of functionally compromised S256-phosphorylated FoxO1+ APCs, and an increased frequency of IgM+CD21+ B cells, which enlarged the marginal zone (MZ). Enlargement of MHCII+CD11b+ APCs ensured favourable conditions for their communication with IgM+ B cells in the MZ. The reduced expression of ICOSL and CXCR5 by APCs after IGF1R inhibition led to impaired T cell control, which resulted in autoreactivity of extra-follicular B cells and autoantibody production. In the clinical setting, the low expression of IGF1R on CD14+ APCs was associated with an involuted FOXO pathway, non-inflammatory cell metabolism and a high IL10 production characteristic for tolerogenic macrophages. Furthermore, autoantibody positivity was associated with low IGF1R signalling in CD14+ APCs.

CONCLUSIONS

In experimental model and in patient material, this study demonstrates that IGF1R plays an important role in preventing autoimmunity. The study raises awareness of that immune tolerance may be broken during therapeutic IGF1R targeting.

The scaffold protein NEDD9 is necessary for leukemia-cell migration and disease progression in a mouse model of chronic lymphocytic leukemia

The scaffold protein NEDD9 is frequently upregulated and hyperphosphorylated in cancers, and is associated with poor clinical outcome. NEDD9 promotes B-cell adhesion, migration and chemotaxis, pivotal processes for malignant development. We show that global or B-cell-specific deletion of Nedd9 in chronic lymphocytic leukemia (CLL) mouse models delayed CLL development, markedly reduced disease burden and resulted in significant survival benefit. NEDD9 was required for efficient CLL cell homing, chemotaxis, migration and adhesion. In CLL patients, peripheral NEDD9 expression was associated with adhesion and migration signatures as well as leukocyte count. Additionally, CLL lymph nodes frequently expressed high NEDD9 levels, with a subset of patients showing NEDD9 expression enriched in the CLL proliferation centers. Blocking activity of prominent NEDD9 effectors, including AURKA and HDAC6, effectively reduced CLL cell migration and chemotaxis. Collectively, our study provides evidence for a functional role of NEDD9 in CLL pathogenesis that involves intrinsic defects in adhesion, migration and homing.

Up-regulation of NSP3 by Oligomeric Aβ Accelerates Neuronal Death Through Cas-independent Rap1A Activation

β-Amyloid (Aβ) plays an important role in the early pathogenesis of Alzheimer's disease (AD). In vitro studies have demonstrated that Aβ oligomers induce hippocampal and neocortical neuronal death. However the neurotoxic mechanisms by which soluble Aβ oligomers cause neuronal damage and death remain to be fully elucidated. To this end, we analyzed the gene expression profile of rat cerebral cortical neurons treated with Aβ oligomers in vitro. Aβ treatment induced the expression of novel SH2-containing protein 3 (NSP3), an adaptor molecule interacting with Cas family proteins. NSP3 expression was upregulated not only in oligomeric-Aβ-treated cultured neurons but also in the neocortex of aged Tg2576 mice. NSP3 overexpression in cultured cortical neurons accelerated neuronal death. The C-terminal region of NSP3 unbound to a Cas protein was necessary for the NSP3-induced acceleration of neuronal death, as was Cas-independent Rap1A activation downstream of NSP3. Moreover, NSP3 RNAi knockdown partially rescued Aβ-oligomer-treated neurons. These results indicate that NSP3 upregulation by soluble Aβ oligomers may accelerate neuronal death via Cas-independent Rap1A activation, implicating NSP3 in the pathogenesis of AD.

Monocyte Adhesion and Plaque Recruitment During Atherosclerosis Development Is Regulated by the Adapter Protein Chat-H/SHEP1

OBJECTIVE

The chronic inflammation associated with atherosclerosis is caused by lipid deposition followed by leukocyte recruitment to the arterial wall. We previously showed that the hematopoietic cell-specific adaptor protein Cas- and Hef1-associated signal transducer hematopoietic isoform (Chat-H)/SHEP1 regulated lymphocyte adhesion and migration. In this study, we analyzed the role of Chat-H in atherosclerosis development.

APPROACH AND RESULTS

Using Chat-H-deficient bone marrow transplantation in low-density lipoprotein receptor-deficient mice, we found that Chat-H regulated atherosclerotic plaque formation. Chat-H deficiency in hematopoietic cells associated with lower plaque complexity and fewer leukocytes in the lesions, whereas myeloid-specific deletion of Chat-H was sufficient for conferring atheroprotection. Chat-H deficiency resulted in reduced recruitment of classical Ly6c(high) and nonclassical Ly6c(low) monocytes to the plaques, which was accompanied by increased numbers of both monocyte subsets in the blood. This associated with defective adhesion of Chat-H-deficient Ly6c(high) and Ly6c(low) monocytes to vascular cell adhesion molecule-1 in vitro and impaired infiltration of fluorescent bead-loaded monocytes to atherosclerotic plaques. In contrast, Chat-H was dispensable for CX3CL1 and CCR1/CCR5-dependent migration of monocytes.

CONCLUSIONS

Our findings highlight Chat-H as a key protein that regulates atherosclerosis development by controlling monocyte adhesion and recruitment to the plaques and identify a novel target that may be exploited for treating atherosclerosis.

Investigation of binding phenomenon of NSP3 and p130Cas mutants and their effect on cell signalling

Members of the novel SH2-containing protein (NSP3) and Crk-associated substrate (p130Cas) protein families form a multi-domain signalling platforms that mediate cell signalling process. We analysed the damaging consequences of three mutations, each from NSP3 (NSP3(L469R), NSP3(L623E), NSP3(R627E)) and p130Cas (p130Cas(F794R), p130Cas(L787E), p130Cas(D797R)) protein with respect to their native biological partners. Mutations depicted notable loss in interaction affinity towards their corresponding biological partners. NSP3(L469R) and p130Cas(D797R) mutations were predicted as most prominent in docking analysis. Molecular dynamics (MD) studies were conducted to evaluate structural consequences of most prominent mutation in NSP3 and p130Cas obtained from the docking analysis. MD analysis confirmed that mutation in NSP3(L469R) and p130Cas(D797R) showed significant structural deviation, changes in conformations and increased flexibility, which in turn affected the binding affinity with their biological partners. Moreover, the root mean square fluctuation has indicated a rise in fluctuation of residues involved in moderate interaction acquired between the NSP3 and p130Cas. It has significantly affected the binding interaction in mutant complexes. The results obtained in this work present a detailed overview of molecular mechanisms involved in the loss of cell signalling associated with NSP3 and p130Cas protein.

Association of the breast cancer antiestrogen resistance protein 1 (BCAR1) and BCAR3 scaffolding proteins in cell signaling and antiestrogen resistance

Most breast cancers are estrogen receptor-positive and treated with antiestrogens, but aberrant signaling networks can induce drug resistance. One of these networks involves the scaffolding protein BCAR1/p130CAS, which regulates cell growth and migration/invasion. A less investigated scaffolding protein that also confers antiestrogen resistance is the SH2 domain-containing protein BCAR3. BCAR1 and BCAR3 bind tightly to each other through their C-terminal domains, thus potentially connecting their associated signaling networks. However, recent studies using BCAR1 and BCAR3 interaction mutants concluded that association between the two proteins is not critical for many of their interrelated activities regulating breast cancer malignancy. We report that these previously used BCAR mutations fail to cause adequate loss-of-function of the complex. By using structure-based BCAR1 and BCAR3 mutants that lack the ability to interact, we show that BCAR3-induced antiestrogen resistance in MCF7 breast cancer cells critically depends on its ability to bind BCAR1. Interaction with BCAR3 increases the levels of phosphorylated BCAR1, ultimately potentiating BCAR1-dependent antiestrogen resistance. Furthermore, antiestrogen resistance in cells overexpressing BCAR1/BCAR3 correlates with increased ERK1/2 activity. Inhibiting ERK1/2 through overexpression of the regulatory protein PEA15 negates the resistance, revealing a key role for ERK1/2 in BCAR1/BCAR3-induced antiestrogen resistance. Reverse-phase protein array data show that PEA15 levels in invasive breast cancers correlate with patient survival, suggesting that PEA15 can override ERK1/2 activation by BCAR1/BCAR3 and other upstream regulators. We further uncovered that the BCAR3-related NSP3 can also promote antiestrogen resistance. Thus, strategies to disrupt BCAR1-BCAR3/NSP3 complexes and associated signaling networks could ultimately lead to new breast cancer therapies.

Experimental infection of dogs with H3N2 canine influenza virus from China

Canine influenza virus (CIV) is an emerging pathogen that causes acute respiratory disease in dogs. The aim of this study was to investigate the pathogenicity of A/canine/Jiangsu/06/2010 (H3N2) virus isolated in China. Nine dogs were inoculated intranasally with 107.95 of 50% egg infectious dose (EID50) of the virus. The onset of clinical signs and virus shedding was observed on day 1 post-infection (p.i.). The peak clinical score occurred between days 4 and 6 p.i. The experimentally infected dogs were found to shed virus not only via the respiratory tract but also via the digestive tract. Viral RNA could be detected in multiple organs including the trachea, lung, liver, spleen, kidney, brain and duodenum. All the sampled organs from infected dogs showed significant lesions and viral antigen staining. The results differed from those reporting using previous CIV strains; the Chinese isolate could induce extrapulmonary infection and cause extensive lesions in dogs.

NSP-CAS Protein Complexes: Emerging Signaling Modules in Cancer

The CAS (CRK-associated substrate) family of adaptor proteins comprises 4 members, which share a conserved modular domain structure that enables multiple protein-protein interactions, leading to the assembly of intracellular signaling platforms. Besides their physiological role in signal transduction downstream of a variety of cell surface receptors, CAS proteins are also critical for oncogenic transformation and cancer cell malignancy through associations with a variety of regulatory proteins and downstream effectors. Among the regulatory partners, the 3 recently identified adaptor proteins constituting the NSP (novel SH2-containing protein) family avidly bind to the conserved carboxy-terminal focal adhesion-targeting (FAT) domain of CAS proteins. NSP proteins use an anomalous nucleotide exchange factor domain that lacks catalytic activity to form NSP-CAS signaling modules. Additionally, the NSP SH2 domain can link NSP-CAS signaling assemblies to tyrosine-phosphorylated cell surface receptors. NSP proteins can potentiate CAS function by affecting key CAS attributes such as expression levels, phosphorylation state, and subcellular localization, leading to effects on cell adhesion, migration, and invasion as well as cell growth. The consequences of these activities are well exemplified by the role that members of both families play in promoting breast cancer cell invasiveness and resistance to antiestrogens. In this review, we discuss the intriguing interplay between the NSP and CAS families, with a particular focus on cancer signaling networks.

NSP-Cas protein structures reveal a promiscuous interaction module in cell signaling

NSP and Cas family proteins form multidomain signaling platforms that mediate cell migration and invasion through a collection of distinct signaling motifs. Members of each family interact via their respective C-terminal domains, but the mechanism of this association has remained enigmatic. Here we present the crystal structures of the C-terminal domain from the human NSP protein BCAR3 and the complex of NSP3 with p130Cas. BCAR3 adopts the Cdc25-homology fold of Ras GTPase exchange factors, but exhibits a “closed” conformation incapable of enzymatic activity. The NSP3–p130Cas complex structure reveals that this closed conformation is instrumental for interaction of NSP proteins with a focal adhesion-targeting domain present in Cas proteins. This enzyme to adaptor conversion enables high affinity, yet promiscuous, interactions between NSP and Cas proteins and represents an unprecedented mechanistic paradigm linking cellular signaling networks.