Background:The Goodpasture antigen-binding protein (GPBP) and serum amyloid P component (SAP) bind to type IV collagen and are found in plasma. Results: GPBP binds to human SAP. Conclusion: GPBP and SAP form complexes under physiological and pathological conditions. Significance: This interaction might be involved in protein aggregation in Alzheimer disease and the resulting innate immune response.

Background Dysregulation of ceramide and sphingomyelin levels have been suggested to contribute to the pathogenesis of Alzheimer’s disease (AD). Ceramide transfer proteins (CERTs) are ceramide carriers which are crucial for ceramide and sphingomyelin balance in cells. Extracellular forms of CERTs co-localize with amyloid-β (Aβ) plaques in AD brains. To date, the significance of these observations for the pathophysiology of AD remains uncertain. Methods A plasmid expressing CERTL, the long isoform of CERTs, was used to study the interaction of CERTL with amyloid precursor protein (APP) by co-immunoprecipitation and immunofluorescence in HEK cells. The recombinant CERTL protein was employed to study interaction of CERTL with amyloid-β (Aβ), Aβ aggregation process in presence of CERTL, and the resulting changes in Aβ toxicity in neuroblastoma cells. CERTL was overexpressed in neurons by adeno-associated virus (AAV) in a mouse model of familial AD (5xFAD). Ten weeks after transduction, animals were challenged with behavior tests for memory, anxiety, and locomotion. At week 12, brains were investigated for sphingolipid levels by mass spectrometry, plaques, and neuroinflammation by immunohistochemistry, gene expression, and/or immunoassay. Results Here, we report that CERTL binds to APP, modifies Aβ aggregation, and reduces Aβ neurotoxicity in vitro. Furthermore, we show that intracortical injection of AAV, mediating the expression of CERTL, decreases levels of ceramide d18:1/16:0 and increases sphingomyelin levels in the brain of male 5xFAD mice. CERTL in vivo over-expression has a mild effect on animal locomotion, decreases Aβ formation, and modulates microglia by decreasing their pro-inflammatory phenotype. Conclusion Our results demonstrate a crucial role of CERTL in regulating ceramide levels in the brain, in amyloid plaque formation and neuroinflammation, thereby opening research avenues for therapeutic targets of AD and other neurodegenerative diseases.

C1q is the initiator of the classical complement pathway and, as such, is essential for efficient opsonization and clearance of pathogens, altered self-structures, and apoptotic cells. The ceramide transporter protein (CERT) and its longer splicing isoform CERTL are known to interact with extracellular matrix components, such as type IV collagen, and with the innate immune protein serum amyloid P. In this article, we report a novel function of CERT in the innate immune response. Both CERT isoforms, when immobilized, were found to bind the globular head region of C1q and to initiate the classical complement pathway, leading to activation of C4 and C3, as well as generation of the membrane attack complex C5b–9. In addition, C1q was shown to bind to endogenous CERTL on the surface of apoptotic cells. These results demonstrate the role of CERTs in innate immunity, especially in the clearance of apoptotic cells.

Viral gene transfer or transgenic animals are commonly used technologies to alter gene expression in the adult brain, although these approaches lack spatial specificity and are time consuming. We delivered plasmid DNA locally into the brain of adult C57BL/6 mice in vivo by voltage- and current-controlled electroporation. The low current-controlled delivery of unipolar square wave pulses of 125 µA with microstimulation electrodes at the injection site gave 16 times higher transfection rates than a voltage-controlled electroporation protocol with plate electrodes resulting in currents of about 400 mA. Transfection was restricted to the target region and no damage due to the electric pulses was found. Our current-controlled electroporation protocol indicated that the use of very low currents resulting in applied voltages within the physiological range of the membrane potential, allows efficient transfection of nonviral plasmid DNA. In conclusion, low current-controlled electroporation is an excellent approach for electroporation in the adult brain, i.e., gene function can be influenced locally at a high level with no mortality and minimal tissue damage.