TY - JOUR
T1 - Formation, stabilisation and fusion of the readily releasable pool of secretory vesicles
AU - Sørensen, Jakob Balslev
N1 - Keywords: Animals; Calcium; Cell Membrane; Exocytosis; Humans; Secretory Vesicles; Vesicular Transport Proteins
PY - 2004
Y1 - 2004
N2 - Calcium-triggered exocytosis of neurotransmitter or hormone-filled vesicles has developed as the main mechanism for cell-to-cell communication in animals. Consequently, in the course of evolution this form of exocytosis has been optimized for speed. Since many of the maturation processes of vesicles are intrinsically slow, the solution has been to develop a pool of vesicles that are fully matured and can be fused very rapidly upon stimulation. Vesicles in this readily releasable pool are characterized by very low release rate constants at the resting cytosolic [Ca2+] ([Ca2+]i) and very high release rate constants at stimulated [Ca2+]i. Here I review the kinetic and molecular requirements for the existence of such a pool of vesicles, focusing on chromaffin cells of the adrenal medulla. I discuss how the use of assay methods with different time resolution may lead to fundamentally different conclusions about the role of proteins in exocytosis. Finally, I review recent evidence that the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, formed between proteins residing in the vesicle and the plasma membrane, is involved in formation and stabilization of the readily releasable vesicle pool, whereas synaptotagmin, a Ca2+- and phospholipid-binding vesicular protein, is involved in setting the Ca2+ dependence of the fusion process itself. Future studies are likely to focus on the interaction between these two classes of proteins.
AB - Calcium-triggered exocytosis of neurotransmitter or hormone-filled vesicles has developed as the main mechanism for cell-to-cell communication in animals. Consequently, in the course of evolution this form of exocytosis has been optimized for speed. Since many of the maturation processes of vesicles are intrinsically slow, the solution has been to develop a pool of vesicles that are fully matured and can be fused very rapidly upon stimulation. Vesicles in this readily releasable pool are characterized by very low release rate constants at the resting cytosolic [Ca2+] ([Ca2+]i) and very high release rate constants at stimulated [Ca2+]i. Here I review the kinetic and molecular requirements for the existence of such a pool of vesicles, focusing on chromaffin cells of the adrenal medulla. I discuss how the use of assay methods with different time resolution may lead to fundamentally different conclusions about the role of proteins in exocytosis. Finally, I review recent evidence that the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, formed between proteins residing in the vesicle and the plasma membrane, is involved in formation and stabilization of the readily releasable vesicle pool, whereas synaptotagmin, a Ca2+- and phospholipid-binding vesicular protein, is involved in setting the Ca2+ dependence of the fusion process itself. Future studies are likely to focus on the interaction between these two classes of proteins.
U2 - 10.1007/s00424-004-1247-8
DO - 10.1007/s00424-004-1247-8
M3 - Review
C2 - 14997396
SN - 0031-6768
VL - 448
SP - 347
EP - 362
JO - Pflügers Archiv - European Journal of Physiology
JF - Pflügers Archiv - European Journal of Physiology
IS - 4
ER -