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 (<0.6 s) endocytosis, amount-specific compensatory endocytosis (endocytosis = exocytosis) or overshoot endocytosis (endocytosis > 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.

平膜转化为圆形囊泡通常被认为是内吞作用的基础，并产生速度、数量和囊泡大小特定的内吞模式。观察活神经内分泌嗜铬细胞中去极化诱导的胞吐和胞吞膜转化，我们发现平膜通过内陷、Λ 基收缩和 Ω 孔收缩转化为 Λ 形、Ω 形和 O 形囊泡，分别。令人惊讶的是，内吞囊泡的形成主要不是从扁平膜到圆形囊泡的转化，而是钙触发和动力蛋白介导的 (1) 去极化前形成的 Ω 剖面和 (2) 融合孔（称为亲吻和运行） ）。不同的钙流入控制着这些孔闭合的速度、数量和囊泡大小，导致速度特定的缓慢（超过~6 秒），快速（小于~6 秒）或超快（<0.6 秒）内吞作用、数量特异性补偿性内吞作用（内吞作用 = 胞吐作用）或过冲内吞作用（内吞作用 > 胞吐作用）和大小特异性的大块内吞作用。这些发现揭示了内吞作用、多种内吞模式和胞吐作用-内吞作用耦合的主要膜转化机制，呼吁纠正半个世纪以来的概念，即扁平到圆形的转化主要介导生理刺激后的内吞作用。