Rescuing neuronal cell death by RAIDD- and PIDD- derived peptides and its implications for therapeutic intervention in neurodegenerative diseases

Total recall: the role of PIDDosome components in neurodegeneration

The PIDDosome is a multiprotein complex that includes p53-induced protein with a death domain 1 (PIDD1), receptor-interacting protein-associated ICH-1/CED-3 homologous protein with a death domain (RAIDD), and caspase-2, the activation of which is driven by PIDDosome assembly. In addition to the key role of the PIDDosome in the regulation of cell differentiation, tissue homeostasis, and organogenesis and regeneration, caspase-2, RAIDD and PIDD1 engagement in neuronal development was shown. Here, we focus on the involvement of PIDDosome components in neurodegenerative disorders, including retinal neuropathies, different types of brain damage, and Alzheimer's disease (AD), Huntington's disease (HD), and Lewy body disease. We also discuss pathogenic variants of PIDD1, RAIDD, and caspase-2 that are associated with intellectual, behavioral, and psychological abnormalities, together with prospective PIDDosome inhibition strategies and their potential clinical application.

Molecular basis of neurodevelopmental disorders caused by pathogenic variants of PIDD

PIDDosome formation followed by caspase-2 activation is critical for genotoxic stress-induced apoptotic cell death. Failure of proper caspase-2 activation causes a neurodevelopmental disorder and intellectual disability. R815W, R862W, and Q863stop mutations in p53-induced protein with a death domain (PIDD), a component of the PIDDosome, also lead to this disorder. However, the molecular mechanisms underlying this pathogenesis remain elusive. In this study, we analyzed the molecular mechanisms underlying the pathogenesis of the PIDD DD pathogenic variants R815W, R862W, and Q863stop. We determined that these mutations prevented the interaction between PIDD and RIP-associated Ich-1/Ced-3 homologous protein with a death domain (RAIDD), a molecule that mediates PIDDosome formation. The disruption of this interaction affects PIDDosome formation and caspase-2 activation.

Serum metabolomic analysis reveals key metabolites in drug treatment of central precocious puberty in female children

Precocious puberty (PP) is a common condition among children. According to the pathogenesis and clinical manifestations, PP can be divided into central precocious puberty (CPP, gonadotropin dependent), peripheral precocious puberty (PPP, gonadotropin independent), and incomplete precocious puberty (IPP). Identification of the variations in key metabolites involved in CPP and their underlying biological mechanisms has increased the understanding of the pathological processes of this condition. However, little is known about the role of metabolite variations in the drug treatment of CPP. Moreover, it remains unclear whether the understanding of the crucial metabolites and pathways can help predict disease progression after pharmacological therapy of CPP. In this study, systematic metabolomic analysis was used to examine three groups, namely, healthy control (group N, 30 healthy female children), CPP (group S, 31 female children with CPP), and treatment (group R, 29 female children) groups. A total of 14 pathways (the top two pathways were aminoacyl-tRNA biosynthesis and phenylalanine, tyrosine, and tryptophan biosynthesis) were significantly enriched in children with CPP. In addition, two short peptides (His-Arg-Lys-Glu and Lys-Met-His) were found to play a significant role in CPP. Various metabolites associated with different pathways including amino acids, PE [19:1(9Z)0:0], tumonoic acid I, palmitic amide, and linoleic acid-biotin were investigated in the serum of children in all groups. A total of 45 metabolites were found to interact with a chemical drug [a gonadotropin-releasing hormone (GnRH) analog] and a traditional Chinese medicinal formula (DBYW). This study helps to understand metabolic variations in CPP after drug therapy, and further investigation may help develop individualized treatment approaches for CPP in clinical practice.

Serum Metabonomics Reveals Key Metabolites in Different Types of Childhood Short Stature

Nowadays, short stature (SS) in childhood is a common condition encountered by pediatricians, with an increase in not just a few families. Various studies related to the variations in key metabolites and their biological mechanisms that lead to SS have increased our understanding of the pathophysiology of the disease. However, little is known about the role of metabolite variation in different types of childhood SS that influence these biological processes and whether the understanding of the key metabolites from different types of childhood SS would predict the disease progression better. We performed a systematic investigation using the metabonomics method and studied the correlation between the three groups, namely, the control, idiopathic short stature (ISS), and short stature due to growth hormone deficiency (GHD). We observed that three pathways (viz., purine metabolism, sphingolipid signaling pathway, and sphingolipid metabolism) were significantly enriched in childhood SS. Moreover, we reported that two short peptides (Thr Val Leu Thr Ser and Trp Ile Lys) might play a significant role in childhood SS. Various metabolites in different pathways including 9,10-DiHOME, 12-HETE, 12(13)-EpOME, arachidonic acid methyl ester, glycerophospho-N-arachidonoyl ethanolamine, curvulinic acid (2-acetyl-3,5-dihydroxyphenyl acetic acid), nonanoic acid, and N'-(2,4-dimethylphenyl)-N-methylformamidine in human serum were compared between 60 children diagnosed with SS and 30 normal-height children. More investigations in this area may provide insights and enhance the personalized treatment approaches in clinical practice for SS by elucidating pathophysiology mechanisms of experimental verification.

Uncovering the PIDDosome and caspase-2 as regulators of organogenesis and cellular differentiation

The PIDDosome is a multiprotein complex that drives activation of caspase-2, an endopeptidase originally implicated in apoptosis. Yet, unlike other caspases involved in cell death and inflammation, caspase-2 seems to exert additional versatile functions unrelated to cell death. These emerging roles range from control of transcription factor activity to ploidy surveillance. Thus, caspase-2 and the PIDDosome act as a critical regulatory unit controlling cellular differentiation processes during organogenesis and regeneration. These newly established functions of the PIDDosome and its downstream effector render its components attractive targets for drug-development aiming to prevent fatty liver diseases, neurodegenerative disorders or osteoporosis.

Nanocarriers as a powerful vehicle to overcome blood-brain barrier in treating neurodegenerative diseases: Focus on recent advances

Neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, Huntington disease and amyotrophic lateral sclerosis throw a heavy burden on families and society. Related scientific researches make tardy progress. One reason is that the known pathogeny is just the tip of the iceberg. Another reason is that various physiological barriers, especially blood-brain barrier (BBB), hamper effective therapeutic substances from reaching site of action. Drugs in clinical treatment of neurodegenerative diseases are basically administered orally. And generally speaking, the brain targeting efficiency is pretty low. Nano-delivery technology brings hope for neurodegenerative diseases. The use of nanocarriers encapsulating molecules such as peptides and genomic medicine may enhance drug transport through the BBB in neurodegenerative disease and target relevant regions in the brain for regenerative processes. In this review, we discuss BBB composition and applications of nanocarriers -liposomes, nanoparticles, nanomicelles and new emerging exosomes in neurodegenerative diseases. Furthermore, the disadvantages and the potential neurotoxicity of nanocarriers according pharmacokinetics theory are also discussed.

RAIDD mutations underlie the pathogenesis of thin lissencephaly (TLIS)

Abnormal regulation of caspase-2-mediated neuronal cell death causes neurodegenerative diseases and defective brain development. PIDDosome is caspase-2 activating complex composed of PIDD, RAIDD, and caspase-2. Recent whole-exome sequencing study showed that the RAIDD mutations in the death domain (DD), including G128R, F164C, R170C, and R170H mutations, cause thin lissencephaly (TLIS) by reducing caspase-2-mediated neuronal apoptosis. Given that the molecular structure of the RAIDD DD:PIDD DD complex is available, in this study, we analyzed the molecular mechanisms underlying TLIS caused by the RAIDD TLIS variants by performing mutagenesis and biochemical assays.