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Abstract: PO1701

Neurexin1α Containing Splice Site 4 Interacts with Nephrin and Contributes to Maintenance of the Integrity of Podocyte Slit Diaphragm

Session Information

Category: Glomerular Diseases

  • 1204 Podocyte Biology

Authors

  • Fukusumi, Yoshiyasu, Department of Cell Biology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
  • Yasuda, Hidenori, Department of Cell Biology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
  • Zhang, Ying, Department of Cell Biology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
  • Kawachi, Hiroshi, Department of Cell Biology, Kidney Research Center, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
Background

Neurexins (NRXNs) are synaptic cell adhesion molecules having essential roles in the assembly and maturation of synapses. It is known that NRXN1α contains 6 splicing sites (SS)s, and multiple splicing variants were diffusely expressed in neuronal tissues. We have previously reported that NRXN1α is expressed at slit diaphragm (SD), a cell-cell junction of podocyte, and is downregulated in injured podocytes. The report also showed that NRXN1α expressed in podocytes is a unique variant containing SS1, 3, 4, and 5, which is a rare variant in neural tissues (Am J Physiol, 300:R340, 2011). However, the role of NRXN1α at SD is not well understood yet.

Methods

The interaction of NRXN1α with SD-associated molecules was analyzed by the immunoprecipitation (IP) assay. The function and structure of SD of NRXN1α KO mice were precisely analyzed.

Results

The interaction of NRXN1α with SD molecules such as nephrin and ephrin-B1 was detected by the IP assay with rat glomerular lysates. IP assay with the HEK cell expression systems showed NRXN1α containing SS4 interacted with nephrin, but NRXN1α lacking SS4 did not. The interaction between NRXN1α and nephrin was dissociated, if nephrin was phosphorylated. The interaction of NRXN1α with ephrin-B1 was not detected in the HEK system, suggesting NRXN1α interacts with ephrin-B1 via nephrin. Abnormal proteinuria (92.1 mg/day vs. 23.8 mg/day, p<0.05) and clear alterations in the expression of major SD components including nephrin, ephrin-B1 and podocin were detected at the age of 20 weeks of NRXN1α KO mice (IF score; nephrin, 2.68 vs. 3.83, p<0.05: ephrin-B1, 2.68 vs. 3.84, p<0.05: podocin, 2.78 vs. 3.58, p<0.05), although these alterations were not detected at the age of 10 weeks. The phenotypes of the KO mice suggest NRXN1α does not play a major role for formation of SD but contributes to the maintenance of the integrity of SD at an elderly age.

Conclusion

Neurexin1α containing SS4 interacts with nephrin, and is a novel SD component. NRXN1α contributes to maintenance of the function and the molecular integrity of SD. It is conceivable that downregulation of NRXN1α participates in the development of podocyte injury onset at an elderly age.

Funding

  • Government Support – Non-U.S.