Carboxymethylation of CRMP2 is associated with decreased Schwann cell myelination efficiency

Association between enhanced carbonyl stress and decreased apparent axonal density in schizophrenia by multimodal white matter imaging

Carbonyl stress is a condition featuring increased rich reactive carbonyl compounds, which facilitate the formation of advanced glycation end products including pentosidine. We previously reported the relationship between enhanced carbonyl stress and disrupted white matter integrity in schizophrenia, although which microstructural component is disrupted remained unclear. In this study, 32 patients with schizophrenia (SCZ) and 45 age- and gender-matched healthy volunteers (HC) were recruited. We obtained blood samples for carbonyl stress markers (plasma pentosidine and serum pyridoxal) and multi-modal magnetic resonance imaging measures of white matter microstructures including apparent axonal density (intra-cellular volume fraction (ICVF)) and orientation (orientation dispersion index (ODI)), and inflammation (free water (FW)). In SCZ, the plasma pentosidine level was significantly increased. Group comparison revealed that mean white matter values were decreased for ICVF, and increased for FW. We found a significant negative correlation between the plasma pentosidine level and mean ICVF values in SCZ, and a significant negative correlation between the serum pyridoxal level and mean ODI value in HC, regardless of age. Our results suggest an association between enhanced carbonyl stress and axonal abnormality in SCZ.

Enhanced carbonyl stress and disrupted white matter integrity in schizophrenia

Carbonyl stress is a state caused by an increase in rich reactive carbonyl compounds (RCOs); RCOs facilitate the formation of advanced glycation end products (AGEs), which are associated with various age-related illnesses. Recently, enhanced carbonyl stress and lower levels of pyridoxal, a kind of vitamin B6 that scavenges RCOs, have been shown to be associated with schizophrenia. Meanwhile, lower levels of pyridoxal have been reported to decrease myelination through the biochemical process of carbonyl stress. Despite a number of reports on white matter disruption in schizophrenia, it is unclear whether this disruption is related to enhanced carbonyl stress. Therefore, we investigated the relationship between carbonyl stress and white matter integrity in schizophrenia using diffusion tensor imaging. A total of 53 patients with schizophrenia and 83 age- and gender-matched healthy controls were recruited. We used plasma pentosidine, an AGE, and serum pyridoxal as carbonyl stress markers. Between-group differences in these carbonyl stress markers and their relationships with white matter integrity were investigated using Tract-Based Spatial Statistics. In the schizophrenia group, plasma pentosidine level was significantly higher and serum pyridoxal level was lower than those of controls. There was a significant negative correlation between plasma pentosidine and white matter integrity in the schizophrenia group, but not in the control group. Our findings suggest that enhanced carbonyl stress is a possible underlying mechanism of white matter microstructural disruption in schizophrenia.

Dysregulation of CRMP2 Post-Translational Modifications Drive Its Pathological Functions

Collapsin response mediator proteins (CRMPs) are a family of ubiquitously expressed, homologous phosphoproteins best known for coordinating cytoskeletal formation and regulating cellular division, migration, polarity, and synaptic connection. CRMP2, the most studied of the five family members, is best known for its affinity for tubulin heterodimers and function in regulating the microtubule network. These functions are tightly regulated by post-translational modifications including phosphorylation, SUMOylation, oxidation, and O-GlcNAcylation. While CRMP2's physiological functions rely mostly on its non-phosphorylated state, dysregulation of CRMP2 phosphorylation and SUMOylation has been reported to be involved in the pathophysiology of multiple diseases including cancer, chronic pain, spinal cord injury, neurofibromatosis type 1, and others. Here, we provide a consolidated update on what is known about CRMP2 signaling and function, first focusing on axonal growth and neuronal polarity, then illustrating the link between dysregulated CRMP2 post-translational modifications and diseases. We additionally discuss the roles of CRMP2 in non-neuronal cells, both in the CNS and regions of the periphery. Finally, we offer thoughts on the therapeutic implications of modulating CRMP2 function in a variety of diseases.