EMAC, Retromer, and VSRs: do they connect?

Area of Science:

• Plant cell biology
• Molecular and cell biology
• Membrane trafficking

Background:

• Eukaryotic endomembrane trafficking shares commonalities, enabling hypothesis generation in plants based on yeast and mammalian models.
• Novel plant cellular compartments with unique protein complex localizations necessitate cautious interpretation of trafficking mechanisms.
• The recently identified ER and microtubule-associated compartment (EMAC) presents such a case.

Purpose of the Study:

• To critically evaluate the proposed retrograde transport of vacuolar sorting receptors (VSRs) to the EMAC via retromer vesicles.
• To highlight discrepancies between proposed models and existing literature on plant retromer composition, localization, and function.
• To address recent contradictory findings regarding VSR trafficking in plants.

Main Methods:

• Literature review and critical analysis of existing data on plant retromer and VSR trafficking.
• Comparison of plant retromer models with those from yeast and mammalian systems.
• Re-evaluation of the EMAC's role in intracellular trafficking pathways.

Main Results:

• The postulation of EMAC as a recipient of VSRs via retromer vesicles is based on non-plant models and overlooks specific plant literature.
• Plant retromer's composition and function may deviate from the conserved pentameric complex (retromer core and sorting nexins) model.
• Recent studies present findings that contradict the proposed VSR trafficking pathway to EMAC.

Conclusions:

• Current models of VSR trafficking to EMAC in plants require revision based on plant-specific retromer characteristics.
• Plant retromer may not function identically to its counterparts in yeast and mammals, necessitating a re-examination of its role in VSR sorting.
• Further research is needed to elucidate the precise mechanisms of VSR trafficking and the function of EMAC in plant cells.