Pacap Acts As A Transmitter At The Sympatho-adrenal Synapse Under The Acute Stress Response

Abstract

Bis(monoacylglycero)phosphate (BMP) is an unusually shaped, negatively charged phospholipid found in elevated concentrations in the late endosomes. The unusual structure and stereochemistry of BMP are thought to play important roles in the endosome, including structural integrity, endosome maturation, and lipid/protein sorting and trafficking. We have utilized dynamic light scattering, fluorescence spectroscopy and transmission electron microscopy to characterize the morphology and size of BMP hydrated dispersions and extruded vesicles. We find that the morphology of hydrated BMP dispersions varies with pH, forming highly structured, clustered dispersions of 500 nm in size at neutral pH 7.4. However, at acidic pH 4.5, spontaneous hydrolysis of BMP occurs, altering the vesicle morphology to spherically shaped dispersions. BMP vesicles are also significantly smaller in diameter than palmitoyloleoylglycerophosphocholine (POPC) vesicles. In a stability assay using dynamic light scattering measurements to compare and monitor 30 nm extruded vesicles of BMP, POPC, and POPG over a 5 week period, we find that BMP vesicles do not fuse to form larger structures. BMP also forms lamellar vesicles evidenced by the fluorescence leakage assay studies. These results shed light on the possibility that the biosynthesis of BMP and the increasing acidity during the maturation process of late endosomes play an important role in the formation of intraendosomal vesicular bodies.