Biology subjects

Yakunin, I.

Publications and source records attributed to Yakunin, I..

3 recordsLinked to original sources

bioRxiv2025

The Golgi vesicle tether p115/USO1 can bind directly to the ER exit site organiser Sec16A

Newly-made secretory and membrane proteins exit the endoplasmic reticulum (ER) in COPII vesicles that form at specialised ER exit sites. These exit sites are typically near to the early Golgi compartments that receive these vesicles. A key player in the delivery of vesicles to the early Golgi is p115 (USO1), a homodimer with a folded head domain and a coiled-coil tail that is anchored to Golgi membranes. p115 has been shown to capture vesicles and to bind to SNARE proteins to promote membrane fusion. Here we report that the head domain of human p115 can bind directly to Sec16A, a large scaffolding protein that organises ER sites and promotes COPII vesicle formation. Structural prediction and deletion mapping define the region of interaction to a conserved motif in the unstructured N-terminal region of Sec16A, and mutations in p115 that block motif binding reduce the efficiency of secretion. This interaction could potentially allow a subset of p115 molecules to reach across from the early Golgi to the ER exit sites to contribute to the large-scale organisation of the early secretory pathway.

cell biology↗

bioRxiv2023

Recruitment of PI4KIIIbeta to the Golgi by ABCD3 is dependent on an upstream pathway of a SNARE complex and golgins

ACBD3 is a protein localised to the Golgi apparatus and recruits other proteins, such as PI4KIII{beta}, to the Golgi. However, the mechanism through which ACBD3 itself is recruited to the Golgi is poorly understood. This study demonstrates there are two mechanisms for ACBD3 recruitment to the Golgi. First, we identified that an MWT374-376 motif in the unique region upstream of the GOLD domain in ACBD3 is essential for Golgi localisation. Second, we use unbiased proteomics to demonstrate that ACBD3 interacts with SCFD1, a Sec1/Munc-18 (SM) protein, and a SNARE protein, SEC22B. CRISPR-KO of SCFD1 causes ACBD3 to become cytosolic. We also found that ACBD3 is redundantly recruited to the Golgi apparatus by two golgins: golgin-45 and giantin, which bind to ACBD3 through interaction with the MWT374-376 motif. Taken together, our results demonstrate that ACBD3 is recruited to the Golgi in a two-step sequential process, with the SCFD1-mediated interaction occurring upstream of the interaction with the golgins.

cell biology↗

bioRxiv2021

Discovery of putative Golgi S-Adenosyl methionine transporters reveals the importance of plant cell wall polysaccharide methylation

Polysaccharide methylation, especially that of pectin, is a common and important feature of land plant cell walls. Polysaccharide methylation takes place in the Golgi apparatus and therefore relies on the import of S-adenosyl methionine (SAM) from the cytosol into the Golgi. However, to date, no Golgi SAM transporter has been identified in plants. In this work, we studied major facilitator superfamily members in Arabidopsis that we identified as putative Golgi SAM transporters (GoSAMTs). Knock-out of the two most highly expressed GoSAMTs led to a strong reduction in Golgi-synthesised polysaccharide methylation. Furthermore, solid-state NMR experiments revealed that reduced methylation changed cell wall polysaccharide conformations, interactions and mobilities. Notably, the NMR revealed the existence of pectin egg-box structures in intact cell walls, and showed that their formation is enhanced by reduced methyl-esterification. These changes in wall architecture were linked to substantial growth and developmental phenotypes. In particular, anisotropic growth was strongly impaired in the double mutant. The identification of putative transporters that import SAM into the Golgi lumen in plants provides new insights into the paramount importance of polysaccharide methylation for plant cell wall structure and function.

plant biology↗