PMID:26283797

Mdm1/Snx13 is a novel ER-endolysosomal interorganelle tethering protein.

Nvj3 (Ydr179w-a) is a novel paralog of Mdm1 that localizes to the nucleus-vacuole junction / ER-vacuole membrane contact site, independently of the canonical tether Nvj1.

"both it and Mdm1 localize specifically to NVJs in an Nvj1-independent manner"
Nvj3 is predicted to be soluble and requires Mdm1 for its NVJ localization, redistributing to the cytoplasm in mdm1-deletion cells.

"Nvj3-GFP redistributed into the cytoplasm in mdm1Δ cells, suggesting Nvj3 interacts directly with Mdm1 at NVJs"
The PXA domain is the only domain shared between Mdm1 and Nvj3; the PI3P-binding activity of Mdm1 resides in its separate PX domain.

"the PXA domain is the only domain shared between Mdm1 and Nvj3"

PMID:29146766

Lipid droplet biogenesis is spatially coordinated at ER-vacuole contacts under nutritional stress.

Deletion of MDM1, NVJ3, or both causes lipid-droplet accumulation and a ~2-fold increase in triacylglycerol, implicating Nvj3 in NVJ-associated neutral-lipid metabolism.

"deleting MDM1, NVJ3, or both causes accumulation of LDs in yeast, and a ~2‐fold increase in TAG"
The triacylglycerol increase in the mdm1 nvj3 double mutant is suppressed by deletion of the fatty acyl-CoA synthetase Faa1, linking Mdm1/Nvj3 to lipid droplet production downstream of fatty acyl-CoA activation.

"Deletion of Faa1 in addition to Mdm1 and Nvj3 suppresses the increase in TAG we see in the mdm1 Δ nvj3 Δ double knockout"

PMID:41542480

Nvj3 regulates Dga1-mediated triacylglycerol synthesis and lipid droplet formation at ER contact sites.