PKCγ-Mediated Phosphorylation of CRMP2 Regulates Dendritic Outgrowth in Cerebellar Purkinje Cells

A cryo-electron microscopic approach to elucidate protein structures from human brain microsomes

We recently developed a "Build and Retrieve" cryo-electron microscopy (cryo-EM) methodology, which is capable of simultaneously producing near-atomic resolution cryo-EM maps for several individual proteins from a heterogeneous, multiprotein sample. Here we report the use of "Build and Retrieve" to define the composition of a raw human brain microsomal lysate. From this sample, we simultaneously identify and solve cryo-EM structures of five different brain enzymes whose functions affect neurotransmitter recycling, iron metabolism, glycolysis, axonal development, energy homeostasis, and retinoic acid biosynthesis. Interestingly, malfunction of these important proteins has been directly linked to several neurodegenerative disorders, such as Alzheimer's, Huntington's, and Parkinson's diseases. Our work underscores the importance of cryo-EM in facilitating tissue and organ proteomics at the atomic level.

Novel mutation in exon11 of PRKCG (SCA14): A case report

Introduction: PRKCG mutations have been implicated in the pathogenesis of spinocerebellar ataxia type 14 (SCA14), which is a rare autosomal dominant disease marked by cerebellar degeneration, dysarthria, and nystagmus. Until now, there has never been a report of patients with mutations of c.1232G>C worldwide. Case description: We report a case of a 30-year-old Chinese man with episodic dystaxia, speech disorder, and cognitive impairment; however, his father exclusively exhibited a speech disorder regardless of the same mutation. Whole-exome sequencing revealed a heterozygous c.1232G>C (p.G411A) variant of PRKCG. Conclusion: This case presents an extended genotype and phenotype of SCA14, and emphasizes the importance of gene sequencing in patients with spinocerebellar ataxia.

Transcriptome Profile of a New Mouse Model of Spinocerebellar Ataxia Type 14 Implies Changes in Cerebellar Development

The autosomal dominant inherited spinocerebellar ataxias (SCAs) are a group of neurodegenerative disorders characterized by cerebellar atrophy and loss of Purkinje neurons. Spinocerebellar ataxia type 14 (SCA14) is a rare variant of SCAs caused by missense mutations or deletions in the PRKCG gene encoding the protein kinase C γ (PKCγ). Although mutated PKCγs are responsible for SCA14, it is still unclear exactly how mutated PKCγs are involved in SCA14 pathogenesis. Therefore, it is important to study how PKCγ signaling is altered in the cerebellum, which genes or signaling pathways are affected, and how this leads to neurological disease. In this study, we used a mouse line carrying a knock-in pseudo-substrate domain mutation in PKCγ (PKCγ-A24E) as an SCA14 model and performed RNA sequencing (RNA-seq) analysis at an early developmental timepoint (postnatal day 15) to investigate changes in the gene profile compared to wildtype mice. We analyzed both heterozygous (Het) PKCγ-A24E mice and homozygous (Homo) PKCγ-A24E mice for transcriptomic changes. The Het PKCγ-A24E mice reflects the situation observed in human SCA14 patient, while Homo PKCγ-A24E mice display stronger phenotypes with respect to Purkinje cell development and behavior. Our findings highlight an abundance of modifications affecting genes involved in developmental processes, suggesting that at least a part of the final phenotype is shaped by altered cerebellar development and is not only caused by changes in mature animals.

Widely Targeted Lipidomics and Transcriptomics Analysis Revealed Changes of Lipid Metabolism in Spleen Dendritic Cells in Shrimp Allergy

Shrimp allergy (SA) is pathological type 2 inflammatory immune responses against harmless shrimp protein allergen, which is caused by complex interactions between dendritic cells (DCs) and other immune cells. Lipid metabolism in different DCs states are significantly changed. However, the lipid metabolism of spleen DCs in SA remain ambiguous. In this study, we established a BALB/c mouse shrimp protein extract-induced allergy model to determine the lipid profile of spleen DCs in SA, and the molecular mechanism between lipid metabolism and immune inflammation was preliminarily studied. Spleen DCs were sorted by fluorescence-activated cell sorting, and then widely targeted lipidomics and transcriptomics analysis were performed. Principal component analysis presented the lipidome alterations in SA. The transcriptomic data showed that Prkcg was involved in lipid metabolism, immune system, and inflammatory signaling pathway. In the correlation analysis, the results suggested that Prkcg was positively correlated with triacylglycerol (Pearson correlation coefficient = 0.917, p = 0.01). The lipidomics and transcriptomics integrated pathway analysis indicated the activated metabolic conversion from triacylglycerol to 1,2-diacyl-sn-glycerol and the transmission of lipid metabolism to immune inflammation (from triacylglycerol and ceramide to Prkcg) in SA spleen DCs, and cellular experiments in vitro showed that glyceryl trioleate and C16 ceramide treatment induced immune function alteration in DCs.

Research Progress of Collapse Response Mediator Proteins in Neurodegenerative Diseases

Collapse response mediator proteins (CRMPs) are a family of cytoplasmic phosphorylated proteins, and the mechanism of action has always been the research focus of neurological diseases. Previous studies on the CRMPs family have revealed that CRMPs mediate the growth and development of neuronal cytoskeleton through different signaling pathways in the body. It plays an important role in neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and spinocerebellar ataxia, which has attracted the attention of researchers. This article reviews the recent literature on the biological characteristics and mechanisms of CRMPs in different neurodegenerative diseases.

Serine/threonine kinase 17b (STK17B) signalling regulates Purkinje cell dendritic development and is altered in multiple spinocerebellar ataxias

Serine/threonine kinase 17b (STK17B, also known as DRAK2) is known to be a downstream effector of protein kinase C (PKC) in the immune system, in particular T lymphocytes. PKC activity also plays a critical role for dendritic development and synaptic maturation and plasticity in cerebellar Purkinje cells. We present evidence that STK17B is strongly expressed in mouse cerebellar Purkinje cells starting in the early postnatal period and remaining highly expressed throughout adult stages and that STK17B is a target of PKC phosphorylation in the cerebellum. STK17B overexpression potentiates the morphological changes of Purkinje cells seen after PKC activation, suggesting that it is a downstream effector of PKC. A phosphorylation mimetic STK17B variant induced a marked reduction of Purkinje cell dendritic tree size, whereas the inhibition of STK17B with the novel compound 16 (Cpd16) could partially rescue the morphological changes of the Purkinje cell dendritic tree after PKC activation. These findings show that STK17B signalling is an important downstream effector of PKC activation in Purkinje cells. Furthermore, STK17B was identified as a molecule being transcriptionally downregulated in mouse models of SCA1, SCA7, SCA14 and SCA41. The reduced expression of STK17B in these mouse models might protect Purkinje cell dendrites from the negative effects of overactivated PKC signalling. Our findings provide new insights in the role of STK17B for Purkinje cell dendritic development and the pathology of SCAs.