N-terminal and C-terminal domains of calmodulin mediate FADD and TRADD interaction

Interaction of the Melatonin/Ca2+-CaM Complex with Calmodulin Kinase II: Physiological Importance

Melatonin N-acetyl-5-methoxytriptamine is an ancient molecule which synchronizes the internal biologic activity with the environmental photoperiod. It is synthesized by the pineal gland during the night and released to the general circulation, where it reaches nanomolar concentrations. The indolamine acts through melatonin receptors and binds to different proteins such as calmodulin: a phylogenetically conserved protein which is the main transductor of the calcium signaling. In this review, we will describe evidence supporting that melatonin binds to calmodulin in presence of calcium, and we discuss the effects of this indolamine on the activity of calmodulin kinase II as an inhibitor and as stimulator of calmodulin-dependent protein kinase II activity. We also provide a literature review supporting the relevance of melatonin binding to calmodulin in the regulation of circadian rhythms in unicellular organisms, as well as in neuronal development in mammals as an ancient, conserved mechanism. Finally, we highlight the importance of antioxidant effects of melatonin on calmodulin preservation. SIGNIFICANCE STATEMENT: This review compiled evidence supporting that melatonin binds to calmodulin. We discuss the dual effect of melatonin on the activity of calmodulin kinase II, the possible mechanisms involved, and the relevance on regulation of circadian rhythms and neurodevelopment. Finally, we describe evidence supporting that the binding of melatonin to calmodulin hydrophobic pockets may prevent the oxidation of methionine species with a shielding effect that preserves the functionality of calmodulin.

Functional roles in cell signaling of adaptor protein TRADD from a structural perspective

TRADD participates in various receptor signaling pathways and plays vital roles in many biological activities, including cell survival and apoptosis, in different cellular contexts. TRADD has two distinct functional domains, a TRAF-binding domain at the N-terminus and a death domain (DD) at the C-terminus. The TRAF binding domain of TRADD folds into an α-β plait topology and is mainly responsible for binding TRAF2, while the TRADD-DD can interact with a variety of DD-containing proteins, including receptors and intracellular signaling molecules. After activation of specific receptors such as TNFR1 and DR3, TRADD can bind to the receptor through DD-DD interaction, creating a membrane-proximal platform for the recruitment of downstream molecules to propagate cellular signals. In this review, we highlight recent advances in the studies of the structural mechanism of TRADD adaptor functions for NF-κB activation and apoptosis induction. We also provide suggestions for future structure research related to TRADD-mediated signaling pathways.

Death domain of p75 neurotrophin receptor: a structural perspective on an intracellular signalling hub

The death domain (DD) is a globular protein motif with a signature feature of an all-helical Greek-key motif. It is a primary mediator of a variety of biological activities, including apoptosis, cell survival and cytoskeletal changes, which are related to many neurodegenerative diseases, neurotrauma, and cancers. DDs exist in a wide range of signalling proteins including p75 neurotrophin receptor (p75^NTR ), a member of the tumour necrosis factor receptor superfamily. The specific signalling mediated by p75^NTR in a given cell depends on the type of ligand engaging the extracellular domain and the recruitment of cytosolic interactors to the intracellular domain, especially the DD, of the receptor. In solution, the p75^NTR -DDs mainly form a symmetric non-covalent homodimer. In response to extracellular signals, conformational changes in the p75^NTR extracellular domain (ECD) propagate to the p75^NTR -DD through the disulfide-bonded transmembrane domain (TMD) and destabilize the p75^NTR -DD homodimer, leading to protomer separation and exposure of binding sites on the DD surface. In this review, we focus on recent advances in the study of the structural mechanism of p75^NTR -DD signalling through recruitment of diverse intracellular interactors for the regulation and control of diverse functional outputs.

Tumor Necrosis Factor Receptor Type 1-Associated Death Domain Protein Is a Potential Prognostic Biomarker in Acute Myeloid Leukemia

BACKGROUND

Tumor necrosis factor receptor type 1-associated death domain protein (TRADD) mediates programmed cell death signaling as well as the Fas-induced cell death pathway. The downregulation of TRADD is found to be associated with the occurrence of many cancers. The present study was designed to investigate the association between TRADD and clinicopathologic features as well as its clinical significance in acute myeloid leukemia (AML).

METHODS

Real-time polymerase chain reaction was performed in 100 new AML, 23 AML complete remission patients, and 20 normal individuals. All statistical analysis was performed using SPSS software.

RESULTS

It was found that the expression of TRADD messenger RNA was lower in new AML patients as compared to healthy individuals and complete remission patients (P = 0.00239). Moreover, TRADD messenger RNA levels were associated with clinical factors such as risk classification (P = 0.0023) and complete remission (P = 0.0147). Kaplan-Meier analysis revealed that the AML patients with high TRADD expression had significantly prolonged overall survival and higher complete remission compared with low TRADD expressing patients.

CONCLUSIONS

It is concluded that downregulation of TRADD may be an independent potential prognostic biomarker in AML.

Calmodulin as a protein linker and a regulator of adaptor/scaffold proteins

Calmodulin (CaM) is a universal regulator for a huge number of proteins in all eukaryotic cells. Best known is its function as a calcium-dependent modulator of the activity of enzymes, such as protein kinases and phosphatases, as well as other signaling proteins including membrane receptors, channels and structural proteins. However, less well known is the fact that CaM can also function as a Ca²⁺-dependent adaptor protein, either by bridging between different domains of the same protein or by linking two identical or different target proteins together. These activities are possible due to the fact that CaM contains two independently-folded Ca²⁺ binding lobes that are able to interact differentially and to some degree separately with targets proteins. In addition, CaM can interact with and regulates several proteins that function exclusively as adaptors. This review provides an overview over our present knowledge concerning the structural and functional aspects of the role of CaM as an adaptor protein and as a regulator of known adaptor/scaffold proteins.

SHYCD induces APE1/Ref-1 subcellular localization to regulate the p53-apoptosis signaling pathway in the prevention and treatment of acute on chronic liver failure

Background & Aims: San huang yin chi decoction(SHYCD) is derived from the yin chen hao decoction, a well-known and canonical Chinese medicine formula from the “Treatise on Febrile Diseases”. Over the past decade, SHYCD has been used to treat and prevent the liver cirrhosis and liver failure. In the present study, we investigated the effects of SHYCD for acute on chronic liver failure(ACLF) and explored its potential mechanism. an ACLF rat model, which induced by carbon tetrachloride (CCl4) combined with D-galactosamine (D-GalN) and lipopolysaccharide(LPS), was used and confirmed by B-ultrasound analysis. Rats were randomly divided into control group, model group, SHYCD-H group, SHYCD-M group, SHYCD-L group, AGNHW group. Compared with the ACLF model group, High, medium, and low doses of SHYCD reduced ALT, AST, TBIL, NH3, IL-1β, IL-6, and TNFα expression levels in the serum, Shorten PT and INR time,and increased Fbg content in the whole blood, increased survival rate of the rats, improved liver pathological changes. APE1 / Ref-1 was mainly expressed in the nucleus, but the nucleus and cytoplasm were co-expressed after hepatocyte injury. SHYCD significantly downregulated APE1/Ref-1 expression in the cytoplasm. Increased APE1/Ref-1, Bcl-2, reduced p53, caspase-3, Bax, and Cyt-c in the total protein. Base on the results, we conclused that High, medium, and low doses of SHYCD could be applied in prevention and treatment of ACLF, and dose-dependent. The possible mechanism is to promote the APE1 / Ref-1 from the cytoplasm to the nuclear transfer, regulation of p53 apoptosis signal pathway prevention and treatment of ACLF.