# Vesicular Glutamate Transporter 3 Is Involved in Glutamatergic Signalling in Podocytes

## TL;DR

This study shows that VGLUT3 helps podocytes in the kidney release glutamate, which could be a new target for treating kidney diseases.

## Contribution

The study identifies VGLUT3 as a novel transporter involved in glutamate release in podocytes.

## Key findings

- VGLUT3 and VGLUT1 are expressed in podocytes and colocalize in some vesicles.
- VGLUT3 is associated with exocytotic proteins and clear vesicle-like structures in podocytes.
- Depletion of VGLUT3 reduces glutamate release in response to depolarization.

## Abstract

Glomerular podocytes act as a part of the filtration barrier in the kidney. The activity of this filter is regulated by ionotropic and metabotropic glutamate receptors. Adjacent podocytes can potentially release glutamate into the intercellular space; however, little is known about how podocytes release glutamate. Here, we demonstrated vesicular glutamate transporter 3 (VGLUT3)-dependent glutamate release from podocytes. Immunofluorescence analysis revealed that rat glomerular podocytes and an immortal mouse podocyte cell line (MPC) express VGLUT1 and VGLUT3. Consistent with this finding, quantitative RT-PCR revealed the expression of VGLUT1 and VGLUT3 mRNA in undifferentiated and differentiated MPCs. In addition, the exocytotic proteins vesicle-associated membrane protein 2, synapsin 1, and synaptophysin 1 were present in punctate patterns and colocalized with VGLUT3 in MPCs. Interestingly, approximately 30% of VGLUT3 colocalized with VGLUT1. By immunoelectron microscopy, VGLUT3 was often observed around clear vesicle-like structures in differentiated MPCs. Differentiated MPCs released glutamate following depolarization with high potassium levels and after stimulation with the muscarinic agonist pilocarpine. The depletion of VGLUT3 in MPCs by RNA interference reduced depolarization-dependent glutamate release. These results strongly suggest that VGLUT3 is involved in glutamatergic signalling in podocytes and may be a new drug target for various kidney diseases.