Synapto-pHluorin
Encyclopedia
Synapto-pHluorin is a genetically encoded optical indicator of vesicle release and recycling. It is used in neuroscience
to study transmitter release. It consists of a pH-sensitive form of green fluorescent protein
(GFP) fused to the luminal side of a vesicle-associated membrane protein (VAMP). At the acidic pH inside transmitter vesicles, synapto-pHluorin is non-fluorescent. When vesicles get released, synapto-pHluorin is exposed to the neutral extracellular space and the presynaptic terminal becomes brightly fluorescent. Following endocytosis
, vesicles become re-acidified and the cycle can start again. Chemical alkalinization of all vesicles is often used for normalization of the synapto-pHluorin signals.
in 1998.
In 2006, an improved version was published, using synaptophysin to target the GFP to vesicles.
secretion in beta cells of the pancreas
.
Neuroscience
Neuroscience is the scientific study of the nervous system. Traditionally, neuroscience has been seen as a branch of biology. However, it is currently an interdisciplinary science that collaborates with other fields such as chemistry, computer science, engineering, linguistics, mathematics,...
to study transmitter release. It consists of a pH-sensitive form of green fluorescent protein
Green fluorescent protein
The green fluorescent protein is a protein composed of 238 amino acid residues that exhibits bright green fluorescence when exposed to blue light. Although many other marine organisms have similar green fluorescent proteins, GFP traditionally refers to the protein first isolated from the...
(GFP) fused to the luminal side of a vesicle-associated membrane protein (VAMP). At the acidic pH inside transmitter vesicles, synapto-pHluorin is non-fluorescent. When vesicles get released, synapto-pHluorin is exposed to the neutral extracellular space and the presynaptic terminal becomes brightly fluorescent. Following endocytosis
Endocytosis
Endocytosis is a process by which cells absorb molecules by engulfing them. It is used by all cells of the body because most substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane...
, vesicles become re-acidified and the cycle can start again. Chemical alkalinization of all vesicles is often used for normalization of the synapto-pHluorin signals.
History
Synapto-pHluorin was invented by Gero MiesenböckGero Miesenböck
Gero Miesenböck is Waynflete Professor of Physiology at the University of Oxford and a fellow of Magdalen College. A native of Austria, he received his M.D. from the University of Innsbruck and undertook postdoctoral training with James Rothman...
in 1998.
In 2006, an improved version was published, using synaptophysin to target the GFP to vesicles.
Applications
Synapto-pHluorin is mainly used by neurobiologists to study transmitter release and recycling at presynaptic terminals. It has also been applied to the study of insulinInsulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
secretion in beta cells of the pancreas
Pancreas
The pancreas is a gland organ in the digestive and endocrine system of vertebrates. It is both an endocrine gland producing several important hormones, including insulin, glucagon, and somatostatin, as well as a digestive organ, secreting pancreatic juice containing digestive enzymes that assist...
.