Amperometry and Electron Microscopy show Stress Granules Induce Homotypic Fusion of Catecholamine Vesicles

Abstract

An overreactive stress granule (SG) pathway and long‐lived, stable SGs formation are thought to participate in the progress of neurodegenerative diseases (NDs). To understand if and how SGs contribute to disorders of neurotransmitter release in NDs, we examined the interaction between extracellular isolated SGs and vesicles. Amperometry shows that the vesicular content increases and dynamics of vesicle opening slow down after vesicles are treated with SGs, suggesting larger vesicles are formed. Data from the transmission electron microscope (TEM) clearly shows that a portion of large dense core vesicles (LDCVs) with double/multiple cores appear, thus confirming SGs induce homotypic fusion between LDCVs. This might be a protective step to help cells to survive following high oxidative stress. A hypothetical mechanism is proposed whereby enriched mRNA in the shell of SGs is likely to bind intrinsically disordered protein (IDP) regions of vesicle associated membrane protein (VAMP) driving a disrupted membrane between two closely buddled vesicles to fuse with each other to form double cored vesicles. Our results show that SGs induce homotypic fusion of LDCVs, providing better understanding of how SGs intervene in pathological processes opening new direction to SGs involved neurodegenerative disease.