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  • Differential sorting behavior for soluble and transmembrane cargoes at the trans-Golgi network in endocrine cells.

Differential sorting behavior for soluble and transmembrane cargoes at the trans-Golgi network in endocrine cells.

Molecular biology of the cell (2019-12-12)
Blake H Hummer, Drew Maslar, Margarita Soltero-Gutierrez, Noah F de Leeuw, Cedric S Asensio
ABSTRACT

Regulated secretion of neuropeptides and peptide hormones by secretory granules (SGs) is central to physiology. Formation of SGs occurs at the trans-Golgi network (TGN) where their soluble cargo aggregates to form a dense core, but the mechanisms controlling the sorting of regulated secretory cargoes (soluble and transmembrane) away from constitutively secreted proteins remain unclear. Optimizing the use of the retention using selective hooks method in (neuro-)endocrine cells, we now quantify TGN budding kinetics of constitutive and regulated secretory cargoes. We further show that, by monitoring two cargoes simultaneously, it becomes possible to visualize sorting to the constitutive and regulated secretory pathways in real time. Further analysis of the localization of SG cargoes immediately after budding from the TGN revealed that, surprisingly, the bulk of two studied transmembrane SG cargoes (phogrin and VMAT2) does not sort directly onto SGs during budding, but rather exit the TGN into nonregulated vesicles to get incorporated to SGs at a later step. This differential behavior of soluble and transmembrane cargoes suggests a more complex model of SG biogenesis than anticipated.

MATERIALS
Product Number
Brand
Product Description

Roche
Anti-HA-Biotin, High Affinity (3F10), from rat IgG1
Sigma-Aldrich
Anti-Insulin antibody, Mouse monoclonal, clone K36AC10, purified from hybridoma cell culture