Editing Exocytosis (section)

=== Regulated exocytosis ===
Regulated exocytosis is usually triggered by an increase in the cytosolic free calcium ions (Ca<sup>2+</sup>) concentration involving synaptotagmin and mediated by SNARE proteins.<ref name="Stojilkovic Ca2+-regulated exocytosis"/> SNARE complex is formed by [[Syntaxin|syntaxin-1]] and [[SNAP25]] at the presynaptic plasma membrane and  [[Synaptobrevin|Synaptrobrevin]] (VAMP) at the vesicle membrane. This complex promotes membrane fusion through mechanical force and is driven by [[adenosine triphosphate]] (ATP) - dependent cycle.<ref name="Südhof-2009">{{Cite journal |last1=Südhof |first1=Thomas C. |last2=Rothman |first2=James E. |date=2009-01-23 |title=Membrane Fusion: Grappling with SNARE and SM Proteins |journal=Science |volume=323 |issue=5913 |pages=474–477 |doi=10.1126/science.1161748 |pmc=3736821 |pmid=19164740|bibcode=2009Sci...323..474S }}</ref> Following the docking and priming processes, the calcium sensors that trigger exocytosis might interact either with the SNARE complex or the phospholipid layer in the attaching membranes. The calcium sensors trigger porosomes to open, allowing neurotransmitters to be released into the synaptic cleft. A small percentage of indocrine and neuron cells have vesicles that are ready to fuse immediately upon stimulation. The majority of cells are kept in reserve pools, like [[Microfilament|actin filaments]] in endocrine cells and synapses in neurons.<ref name="Stojilkovic Ca2+-regulated exocytosis"/> This makes sure the vesicles docked are able to undergo a fusion at a rapid rate.<ref>{{Cite journal |last1=Zhang |first1=Minchuan |last2=Augustine |first2=George J. |date=2021-03-16 |title=Synapsins and the Synaptic Vesicle Reserve Pool: Floats or Anchors? |journal=Cells |volume=10 |issue=3 |pages=658 |doi=10.3390/cells10030658 |doi-access=free |pmc=8002314 |pmid=33809712}}</ref>