Proteomics: techniques and applications in neuroscience

Identification of differentially expressed exosome proteins in serum as potential biomarkers for cognitive impairments in cerebral small vessel disease

BACKGROUND

Cognitive impairment arising from cerebral small vessel disease (CSVD) represents a critical subtype of vascular cognitive impairments (VCI) and is the primary cause of vascular dementia. However, identifying reliable clinical and laboratory indicators for this disease remain elusive. We hypothesize that plasma exosome proteins hold the potential to serve as biomarkers for the onset of cognitive dysfunction associated with cerebrovascular diseases.

METHODS

We employed TMT-based proteomics to discern variations in serum exosome proteomes between individuals with cognitive impairments due to CSVD and healthy volunteers.

RESULTS

Each group comprised 18 subjects, and through differential expression analysis, we identified 22 down-regulated and 8 up-regulated proteins between the two groups. Our research revealed 30 differentially expressed plasma exosome proteins, including histone, proteasome, clusterin and coagulation factor XIII, in individuals with cognitive impairments caused by CSVD.

CONCLUSION

The 30 differentially expressed plasma exosome proteins identified in our study are promising as biomarkers for diagnosing cognitive impairments resulting from CSVD. These findings may help us better understand the underlying pathological mechanisms involved in the diseases.

Proteomic Analyses of the Mouse Brain

Proteomics is a scientific field that aims to identify and characterize all proteins within a biological system, including their posttranslational modifications (PTMs), quantitative changes, and protein-protein interactions. Over the last two decades, proteomic approaches have been widely used in neuroscience research, providing multidimensional insights into the biology and pathology of the brain.Here, we present a basic protocol for profiling protein expression in the mouse brain, which involves total protein extraction, fractionation, digestion, and identification through liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). This method is compatible with many prevalent techniques used for protein quantitation, PTM analysis, and protein-protein interaction mapping.

Brain cell type specific proteomics approach to discover pathological mechanisms in the childhood CNS disorder mucolipidosis type IV

Mucolipidosis IV (MLIV) is an ultra-rare, recessively inherited lysosomal disorder resulting from inactivating mutations in MCOLN1, the gene encoding the lysosomal cation channel TRPML1. The disease primarily affects the central nervous system (CNS) and manifests in the first year with cognitive and motor developmental delay, followed by a gradual decline in neurological function across the second decade of life, blindness, and premature death in third or fourth decades. Brain pathology manifestations in MLIV are consistent with hypomyelinating leukodystrophy with brain iron accumulation. Presently, there are no approved or investigational therapies for MLIV, and pathogenic mechanisms remain largely unknown. The MLIV mouse model, Mcoln1-/- mice, recapitulates all major manifestations of the human disease. Here, to better understand the pathological mechanisms in the MLIV brain, we performed cell type specific LC-MS/MS proteomics analysis in the MLIV mouse model and reconstituted molecular signatures of the disease in either freshly isolated populations of neurons, astrocytes, oligodendrocytes, and neural stem cells, or whole tissue cortical homogenates from young adult symptomatic Mcoln1-/- mice. Our analysis confirmed on the molecular level major histopathological hallmarks of MLIV universally present in Mcoln1-/- tissue and brain cells, such as hypomyelination, lysosomal dysregulation, and impaired metabolism of lipids and polysaccharides. Importantly, pathway analysis in brain cells revealed mitochondria-related alterations in all Mcoln1-/- brain cells, except oligodendrocytes, that was not possible to resolve in whole tissue. We also report unique proteome signatures and dysregulated pathways for each brain cell population used in this study. These data shed new light on cell-intrinsic mechanisms of MLIV and provide new insights for biomarker discovery and validation to advance translational studies for this disease.

RNF113A targeted by miR-197 promotes proliferation and inhibits autophagy via CXCR4/CXCL12/AKT/ERK/Beclin1 axis in cervical cancer

Ring Finger Protein 113 (RNF113A), an ubiquitin E3 ligase, is genetically associated with many biological processes, including proliferation, differentiation, cell death, and neurogenesis. Recently, RNF113A has been found to be an abnormal expression in many diseases, such as X-linked trichothiodystrophy syndrome and esophageal cancer. Here, we explore the potential mechanism of RNF113A in the progression of cervical cancer (CC). In this study, we evaluated the expression level and biological function of RNF113A in CC both in vitro and in vivo by bioinformatic prediction, DIA proteomic analysis, compensation experiment, Co-IP, dual-luciferase reporter assay and nude mouse xenograft to identify the RNF113A-associated autophagy pathways involved with tumorigenesis. Consistent with the prediction from biological information analysis, we found that RNF113A was highly expressed in human CC tissues and cells. In addition, this study illustrated that the high expression of RNF113A dramatically promoted proliferation and suppressed autophagy both in vitro and in vivo. In contrast, low expression of RNF113A enhanced autophagy activities and inhibited tumor growth in CC. We also found that miRNA-197, the level of which (negative correlation with RNF113A) declined in human CC, directly restrained the expression of RNF113A. Mechanistically, proteomic and mechanistic assays uncovered that RNF113A confirmed as the direct downstream target of miR-197, promoted proliferation and restrained autophagy in CC not through direct ubiquitination degradation of autophagy marker Beclin1 but via CXCR4/CXCL12/AKT/ERK/Beclin1 signal transduction axis. In summary, we found a new miR-197/RNF113 A/CXCR4/CXCL12/AKT/ERK/Beclin1 regulation pathway that plays an important part in the survival and progression of CC.

Proteomic insights into synaptic signaling in the brain: the past, present and future

Chemical synapses in the brain connect neurons to form neural circuits, providing the structural and functional bases for neural communication. Disrupted synaptic signaling is closely related to a variety of neurological and psychiatric disorders. In the past two decades, proteomics has blossomed as a versatile tool in biological and biomedical research, rendering a wealth of information toward decoding the molecular machinery of life. There is enormous interest in employing proteomic approaches for the study of synapses, and substantial progress has been made. Here, we review the findings of proteomic studies of chemical synapses in the brain, with special attention paid to the key players in synaptic signaling, i.e., the synaptic protein complexes and their post-translational modifications. Looking toward the future, we discuss the technological advances in proteomics such as data-independent acquisition mass spectrometry (DIA-MS), cross-linking in combination with mass spectrometry (CXMS), and proximity proteomics, along with their potential to untangle the mystery of how the brain functions at the molecular level. Last but not least, we introduce the newly developed synaptomic methods. These methods and their successful applications marked the beginnings of the synaptomics era.