Preformed Ω-profile closure and kiss-and-run mediate endocytosis and diverse endocytic modes in neuroendocrine chromaffin cells

• Published in: Neuron (Cambridge, Mass.) Mass.), 2021-10, Vol.109 (19), p.3119-3134.e5
• Main Authors: Shin, Wonchul, Wei, Lisi, Arpino, Gianvito, Ge, Lihao, Guo, Xiaoli, Chan, Chung Yu, Hamid, Edaeni, Shupliakov, Oleg, Bleck, Christopher K.E., Wu, Ling-Gang
• Format: Article
• Language: English
• Subjects: bulk endocytosis; compensatory endocytosis; endocytosis overshoot; exo-endocytosis coupling; fast endocytosis; kiss-and-run; membrane dynamics; slow endocytosis; super-resolution imaging; ultrafast endocytosis
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2021.07.019

Transformation of flat membrane into round vesicles is generally thought to underlie endocytosis and produce speed-, amount-, and vesicle-size-specific endocytic modes. Visualizing depolarization-induced exocytic and endocytic membrane transformation in live neuroendocrine chromaffin cells, we found that flat membrane is transformed into Λ-shaped, Ω-shaped, and O-shaped vesicles via invagination, Λ-base constriction, and Ω-pore constriction, respectively. Surprisingly, endocytic vesicle formation is predominantly from not flat-membrane-to-round-vesicle transformation but calcium-triggered and dynamin-mediated closure of (1) Ω profiles formed before depolarization and (2) fusion pores (called kiss-and-run). Varying calcium influxes control the speed, number, and vesicle size of these pore closures, resulting in speed-specific slow (more than ∼6 s), fast (less than ∼6 s), or ultrafast ( exocytosis), and size-specific bulk endocytosis. These findings reveal major membrane transformation mechanisms underlying endocytosis, diverse endocytic modes, and exocytosis-endocytosis coupling, calling for correction of the half-a-century concept that the flat-to-round transformation predominantly mediates endocytosis after physiological stimulation. [Display omitted] •Preformed Ω-profile pore and fusion pore closure mediates many modes of endocytosis•Modes of endocytosis include ultrafast, fast, slow, bulk, and overshoot mode•These endocytic modes do not reflect the widely believed flat-to-round transition•First real-time visualization of a flat to Λ-, Ω-, and O-shaped endocytic transition Visualizing exo- and endocytosis in live neuroendocrine cells, Shin et al. found that preformed Ω-profile pore closure and fusion pore closure predominantly mediate diverse modes of endocytosis varied in speeds, amounts, and vesicle sizes, calling for correction of the half-a-century concept that flat-to-round membrane transformation primarily mediates endocytosis after stimulation.