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Endocrine cells employ regulated exocytosis of secretory granules to secrete hormones and neurotransmitters. Secretory granule exocytosis depends on spatiotemporal variables such as proximity to the plasma membrane and age, with newly generated granules being preferentially released. Despite recent advances, we lack a comprehensive view of the molecular composition of insulin granules and associated changes over their lifetime. Here, we report a strategy for the purification of insulin secretory granules of distinct age from insulinoma INS-1 cells. Tagging the granule-resident protein phogrin with a cleavable CLIP tag, we obtain intact fractions of age-distinct granules for proteomic and lipidomic analyses. We find that the lipid composition changes over time, along with the physical properties of the membrane, and that kinesin-1 heavy chain (KIF5b) as well as Ras-related protein 3a (RAB3a) associate preferentially with younger granules. Further, we identify the Rho GTPase-activating protein (ARHGAP1) as a cytosolic factor associated with insulin granules.
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http://dx.doi.org/10.1016/j.celrep.2024.113836 | DOI Listing |
Front Endocrinol (Lausanne)
September 2025
Department of Biological Sciences, University of Denver, Denver, CO, United States.
The ability to quantify protein secretion is critical for studying the secretory pathway. This is particularly important in endocrine cells where dysregulated hormone secretion is associated with the development of diseases such as type 2 diabetes. To measure protein secretion, researchers have previously relied on techniques such as ELISA, RIA and Western blot, which all present limitations, including cost and time consumption.
View Article and Find Full Text PDFJ Biosci
September 2025
Cell Metabolism Lab (GA-08), Department of Developmental Biology and Genetics (DBG), Indian Institute of Science (IISc), Bengaluru 560012, India.
In most individuals with type 2 diabetes mellitus (T2DM), aggregation of amylin or islet amyloid polypeptide (IAPP) leads to β-cell apoptosis, impairs glucose-stimulated insulin secretion, and causes islet disorganisation (Cooper . 1987; Westermark and Westermark 2000). Amylin is sorted within the immature secretory granules (ISGs) of pancreatic β-cells and co-secreted with insulin upon nutrient stimulation to regulate metabolism.
View Article and Find Full Text PDFFront Pharmacol
August 2025
School of Public Health, Shaanxi University of Chinese Medicine, Xianyang, China.
Background: Osteoporosis (OP), an age-related skeletal disorder characterized by reduced bone mass and deteriorated microarchitecture, and non-alcoholic fatty liver disease (NAFLD), a metabolic condition primarily driven by obesity and insulin resistance (with age as a modifying factor), were investigated in this study. We aimed to elucidate the correlation between OP and NAFLD-associated lipid metabolism, and determine the therapeutic effects and molecular mechanisms of Kangshujiangu granules (KSJG) on NAFLD pathogenesis.
Methods: Clinical study: 261 patients were stratified by OP T-scores into OP and non-OP groups.
J Cell Biol
October 2025
School of Medical Sciences, Charles Perkins Centre, University of Sydney, Camperdown, Australia.
Insulin granule fusion in pancreatic β cells localizes to where they contact the ECM of the islet capillaries. The mechanism(s) underpinning localization are unclear. Using glucose or high K+ stimulation or the global uncaging of Ca2+, we show granule fusion consistently focused to the β cell-ECM interface, suggesting a specific localization mechanism.
View Article and Find Full Text PDFJ Biol Chem
August 2025
Department of Medicine, Division of Endocrinology, Stanford University, Stanford, CA, USA; Department of Bioengineering, Stanford University, Stanford, CA, USA. Electronic address:
Pathologic loss of insulin-producing pancreatic β-cells is a hallmark of diabetes that is potentially reversible through regenerative therapy. However, existing replication-promoting compounds lack β-cell specificity, limiting their clinical application. To overcome this challenge, we generated βRepZnC, a zinc-chelating replication compound designed to leverage the uniquely high zinc content of β-cells for targeted delivery.
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