Neuronal surface P antigen (NSPA) modulates postsynaptic NMDAR stability through ubiquitination of tyrosine phosphatase PTPMEG

Not Dead Yet

I have been a scientific grasshopper throughout my career, moving from question to question within the domain of lupus. This has proven to be immensely gratifying. Scientific exploration is endlessly fascinating, and succeeding in studies you care about with colleagues and trainees leads to strong and lasting bonds. Science isn't easy; being a woman in science presents challenges, but the drive to understand a disease remains strong.

Neuropsychiatric lupus erythematosus: Focusing on autoantibodies

Patients with systemic lupus erythematosus (SLE) frequently suffer from nervous system complications, termed neuropsychiatric lupus erythematosus (NPLE). NPLE accounts for the poor prognosis of SLE. Correct attribution of NP events to SLE is the primary principle in managing NPLE. The vascular injuries and neuroinflammation are the fundamental neuropathologic changes in NPLE. Specific autoantibody-mediated central nerve system (CNS) damages distinguish NPLE from other CNS disorders. Though the central antibodies in NPLE are generally thought to be raised from the periphery immune system, they may be produced in the meninges and choroid plexus. On this basis, abnormal activation of microglia and disease-associated microglia (DAM) should be the common mechanisms of NPLE and other CNS disturbances. Improved understanding of both characteristic and sharing features of NPLE might yield further options for managing this disease.

Progress in the mechanism of neuronal surface P antigen modulating hippocampal function and implications for autoimmune brain disease

PURPOSE OF REVIEW

The aim of this study was to present a new regulation system in the hippocampus constituted by the neuronal surface P antigen (NSPA) and the tyrosine phosphatase PTPMEG/PTPN4, which provides mechanistic and therapeutic possibilities for cognitive dysfunction driven by antiribosomal P protein autoantibodies in patients with systemic lupus erythematosus (SLE).

RECENT FINDINGS

Mice models lacking the function of NSPA as an E3 ubiquitin ligase show impaired glutamatergic synaptic plasticity, decreased levels of NMDAR at the postsynaptic density in hippocampus and memory deficits. The levels of PTPMEG/PTPN4 are increased due to lower ubiquitination and proteasomal degradation, resulting in dephosphorylation of tyrosines that control endocytosis in GluN2 NMDAR subunits. Adult hippocampal neurogenesis (AHN) that normally contributes to memory processes is also defective in the absence of NSPA.

SUMMARY

NSPA function is crucial in memory processes controlling the stability of NMDAR at PSD through the ubiquitination of PTPMEG/PTPN4 and also through AHN. As anti-P autoantibodies reproduce the impairments of glutamatergic transmission, plasticity and memory performance seen in the absence of NSPA, it might be expected to perturb the NSPA/PTPMEG/PTPN4 pathway leading to hypofunction of NMDAR. This neuropathogenic mechanism contrasts with that of anti-NMDAR antibodies also involved in lupus cognitive dysfunction. Testing this hypothesis might open new therapeutic possibilities for cognitive dysfunction in SLE patients bearing anti-P autoantibodies.

The correlation between proteoglycan 2 and neuropsychiatric systemic lupus erythematosus

The proposed pathogenesis of neuropsychiatric systemic lupus erythematosus (NPSLE) mainly includes ischemia and neuroinflammation mechanisms. Protein encoded by Proteoglycan 2 (PRG2) mRNA is involved in the immune process related to eosinophils, also being found in the placenta and peripheral blood of pregnant women. We evaluated the correlation between PRG2 and NPSLE for the first time and found that PRG2 protein is overexpressed in the serum of patients with NPSLE and correlated with the SLE disease activity index (SLEDAI) subset scores of psychosis. Moreover, we investigated the correlation between hippocampal PRG2 level and hippocampally dependent learning and memory ability in MRL/lpr mice, and discovered that the number of PRG2⁺GFAP⁺ astrocytes in the cortex and hypothalamus and the number of PRG2⁺IBA-1⁺ microglia in the hippocampus and cortex significantly increased in the MRL/lpr mice. These data provided a reference for the follow-up exploration of the role of PRG2 in SLE or other diseases.

Roles of N-Methyl-D-Aspartate Receptors (NMDARs) in Epilepsy

Epilepsy is one of the most common neurological disorders characterized by recurrent seizures. The mechanism of epilepsy remains unclear and previous studies suggest that N-methyl-D-aspartate receptors (NMDARs) play an important role in abnormal discharges, nerve conduction, neuron injury and inflammation, thereby they may participate in epileptogenesis. NMDARs belong to a family of ionotropic glutamate receptors that play essential roles in excitatory neurotransmission and synaptic plasticity in the mammalian CNS. Despite numerous studies focusing on the role of NMDAR in epilepsy, the relationship appeared to be elusive. In this article, we reviewed the regulation of NMDAR and possible mechanisms of NMDAR in epilepsy and in respect of onset, development, and treatment, trying to provide more evidence for future studies.

Cognitive Impairment in SLE: Mechanisms and Therapeutic Approaches

A wide range of patients with systemic lupus erythematosus (SLE) suffer from cognitive dysfunction (CD) which severely impacts their quality of life. However, CD remains underdiagnosed and poorly understood. Here, we discuss current findings in patients and in animal models. Strong evidence suggests that CD pathogenesis involves known mechanisms of tissue injury in SLE. These mechanisms recruit brain resident cells, in particular microglia, into the pathological process. While systemic immune activation is critical to central nervous system injury, the current focus of therapy is the microglial cell and not the systemic immune perturbation. Further studies are critical to examine additional potential therapeutic targets and more specific treatments based on the cause and progress of the disease.