JNK1 activation mediates C5b-9-induced P0 mRNA instability and P0 gene expression in Schwann cells

Pathophysiological Significance of WDR62 and JNK Signaling in Human Diseases

The c-Jun N-terminal kinase (JNK) is highly evolutionarily conserved and plays important roles in a broad range of physiological and pathological processes. The WD40-repeat protein 62 (WDR62) is a scaffold protein that recruits different components of the JNK signaling pathway to regulate several human diseases including neurological disorders, infertility, and tumorigenesis. Recent studies revealed that WDR62 regulates the process of neural stem cell mitosis and germ cell meiosis through JNK signaling. In this review we summarize the roles of WDR62 and JNK signaling in neuronal and non-neuronal contexts and discuss how JNK-dependent signaling regulates both processes. WDR62 is involved in various human disorders via JNK signaling regulation, and may represent a promising therapeutic strategy for the treatment of related diseases.

Dichotomy of complement system: Tumorigenesis or destruction

Complement system proteins, their regulators and endpoint effector complex significantly promote tumor growth by upregulation of oncogenic growth factors, activation of mitogenic signalling pathways and breakage of normal cell cycle. Contrastingly, complement cascades, initiated by anti-tumor therapeutic antibodies, also play a pivotal role in therapy response. This contradictory role of complement system possibly be a very crucial factor for the outcomes of antibody mediated immunotherapies. Herein, we reviewed the twin role of the complement system in cancer and also the genetic variations in complement system genes. Future studies should be focused on the biomarker discovery for the personalised cancer immunotherapies.

Molecules involved in the crosstalk between immune- and peripheral nerve Schwann cells

Schwann cells are the myelinating glial cells of the peripheral nervous system and establish myelin sheaths on large caliber axons in order to accelerate their electrical signal propagation. Apart from this well described function, these cells revealed to exhibit a high degree of differentiation plasticity as they were shown to re- and dedifferentiate upon injury and disease as well as to actively participate in regenerative- and inflammatory processes. This review focuses on the crosstalk between glial- and immune cells observed in many peripheral nerve pathologies and summarizes functional evidences of molecules, regulators and factors involved in this process. We summarize data on Schwann cell's role presenting antigens, on interactions with the complement system, on Schwann cell surface molecules/receptors and on secreted factors involved in immune cell interactions or para-/autocrine signaling events, thus strengthening the view for a broader (patho) physiological role of this cell lineage.

Anti-GD(2) with an FC point mutation reduces complement fixation and decreases antibody-induced allodynia

Monoclonal antibodies against GD(2) ganglioside, such as ch14.18, the human-mouse chimeric antibody, have been shown to be effective for the treatment of neuroblastoma. However, treatment is associated with generalized, relatively opiate-resistant pain. We investigated if a point mutation in ch14.18 antibody (hu14.18K332A) to limit complement-dependent cytotoxicity (CDC) would ameliorate the pain behavior, while preserving antibody-dependent cellular cytotoxicity (ADCC). In vitro, CDC and ADCC were measured using europium-TDA assay. In vivo, allodynia was evaluated by measuring thresholds to von Frey filaments applied to the hindpaws after injection of either ch14.18 or hu14.18K332 into wild type rats or rats with deficient complement factor 6. Other rats were pretreated with complement factor C5a receptor antagonist and tested following ch14.18 injection. The mutation reduces the antibody's ability to activate complement, while maintaining its ADCC capabilities. Injection of hu14.18K322 (1 or 3mg/kg) produced faster resolving allodynia than that engendered by ch14.18 (1mg/kg). Injection of ch14.18 (1mg/kg) into rats with C6 complement deficiency further reduced antibody-induced allodynia, while pre-treatment with complement factor C5a receptor antagonist completely abolished ch14.18-induced allodynia. These findings showed that mutant hu14.18 K322 elicited less allodynia than ch14.18 and that ch14.18-elicited allodynia is due to activation of the complement cascade: in part, to formation of membrane attack complex, but more importantly to release of complement factor C5a. Development of immunotherapeutic agents with decreased complement-dependent lysis while maintaining cellular cytotoxicity may offer treatment options with reduced adverse side effects, thereby allowing dose escalation of therapeutic antibodies.

Involvement of the c-jun N-terminal kinases JNK1 and JNK2 in complement-mediated cell death

Cell death and survival signals activated by the complement membrane attack complex C5b-9 play important roles in complement-associated diseases and in antibody-based cancer therapy. Here, we investigated the involvement of the JNK mitogen-activated protein kinase in C5b-9-induced cell lysis. Necrotic-type cell death regulation by JNK1 and JNK2 was selectively studied in mouse fibroblasts and human K562, HeLa and 293T cells. C5b-9 induced higher JNK activation than C5b-8. Pretreatment with a JNK inhibitor reduced cell sensitivity to complement-mediated lysis. KO cells deficient in either JNK1 or JNK2 were less sensitive to lysis than WT cells. This correlated with lower C3 and C5b-9 deposition on KO cells. Furthermore, silencing of JNK1 or JNK2 expression by RNA interference decreased cell lysis by complement. Reconstitution of JNK2 into JNK2-/- cells and over expression of JNK2 in WT cells increased C3 and C5b-9 deposition as well as cell sensitivity to complement-mediated lysis. Pretreatment of cells with the phosphotyrosine phosphatase inhibitor phenylarsine oxide increased JNK activation and JNK-dependent complement-mediated necrotic death of WT and JNK2-/- KO cells but not of JNK1-/- KO cells. The JNK inhibitor and PAO had no effect on complement-mediated lysis in cells lacking Bid, suggesting involvement of Bid in the JNK lytic pathway. Our results demonstrate that complement C5b-9 induce a JNK/Bid-dependent and JNK-independent necrotic cell death. Both JNK1 and JNK2 have cytotoxic potential, however JNK2 is the primary signal transducer.

Innate immunity in the nervous system

The complement (C) system plays a central role in innate immunity and bridges innate and adaptive immune responses. A fine balance of C activation and regulation mediates the elimination of invading pathogens and the protection of the host from excessive C deposition on healthy tissues. If this delicate balance is disrupted, the C system may cause injury and contribute to the pathogenesis of various diseases, including neurodegenerative disorders and neuropathies. Here we review evidence indicating that C factors and regulators are locally synthesized in the nervous system and we discuss the evidence supporting the protective or detrimental role of C activation in health, injury, and disease of the nerve.

Emerging role of mitogen-activated protein kinases in peripheral neuropathies

Among the different families of intracellular molecules that can be modulated during cell damage and repair, mitogen-activated protein kinases (MAPKs) are particularly interesting because they are involved in several intracellular pathways activated by injury and regeneration signals. Despite most of the studies have been performed in non-neurological models, recently a causal role for MAPKs has been postulated in central nervous system disorders. However, also in some peripheral neuropathies, MAPK changes can occur and these modifications might be relevant in the pathogenesis of the damage as well as during regeneration and repair. In this review, the current knowledge on the role of MAPKs in peripheral neuropathies will be discussed.