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bioRxiv · 10.1101/2020.07.17.209122

The Step-Wise C-Truncation and Transport of ESyt3 to Lipid Droplets Reveals a Mother Primordial Cisterna

Lalioti, V. S.·Beznoussenko, G. V.·Mironov, A. A.·Sandoval, I. V.
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Abstract

Extended synaptotagmins (E-Syts) are endoplasmic reticulum (ER) proteins consisting of an SMP domain and multiple C2 domains that bind phospholipids and Ca2+. E-Syts create contact junctions between the ER and plasma membrane to facilitate lipid exchange. During adipocyte differentiation, the proteasome-based removal of the C2C domain results in targeting of E-Syt3 to the primordial cisterna, a previously undescribed giant annular organelle that mothers the LDs. Further cleavage causes the E-Syt3 relocation to the surface of LDs. Fragmentation of the primordial cisterna and LD budding into its lumen are early events in the biogenesis of LDs in the 3T3-L1 adipocyte. Electron tomography-based 3D reconstruction of the fragmented primordial cisterna revealed patches of a tightly packed E-Syt3-rich network of varicose tubules in close contact with young LDs. Esyt3 binds avidly phosphatidylethanolamine through its SMP domain, a main component of the LD membrane that fosters LD biogenesis. Repression of E-Syt3 effectively inhibits LD biogenesis and growth.

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Lalioti, V. S., Beznoussenko, G. V., Mironov, A. A., Sandoval, I. V.. 2020-07-18. The Step-Wise C-Truncation and Transport of ESyt3 to Lipid Droplets Reveals a Mother Primordial Cisterna. https://doi.org/10.1101/2020.07.17.209122

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