GCaMP
Encyclopedia
GCaMP is a genetically encoded calcium indicator
, or GECI. GECIs are designed to show the calcium ion status of a tissue or medium and are either transfected into cell lines or via transgenic crosses. GCaMP is created from a fusion of green fluorescent protein
(GFP), calmodulin
, and M13
(Hires).
GFP is circularly permuted so that the N- and C-termini are fused, creating a new terminus in the middle of the protein. Fused to the new terminus is calmodulin (CaM) and the M13 domain of a myosin light chain kinase (Nakai). Calmodulin is a symmetrical, hinge-like protein that binds to four calcium ions via E-F motifs. When calcium is present, CaM undergoes a conformational change, and the hinge region is able to bind helical peptide chains on target proteins, such as M13. When calcium is not present, there is a hole from the outside of the barrel into the chromophore
, and GFP fluoresces dimly. However when calcium is present, the hole is plugged and GFP fluorescence increases (Hires). Therefore, GCaMP provides imaging of cellular processes, such as action potentials.
Due to its modularity, modifications in the different components of GCaMP have been made to achieve imaging that is brighter, faster, and has better signal-to-noise detection (Hires). Previous research has shown that amino acid substitutions in GFP could enhance folding activity and therefore increase fluorescence. These adaptations are seen in derivatives of GCaMP, such as GCaMP2 and GCaMP3. This “superfolder GFP” has also been utilized in GCaMP-HS to create improvements in brightness and signal amplitude (Muto). Since GFP has been modified, it is also probable that modifications could be made in calmodulin and its target proteins. However, this hypothesis has yet to be proven.
This imaging technique enables monitoring of neurons via action potentials, which would otherwise require large amounts of electrodes or electro-imaging. GCaMP3 has experimentally shown to have high signal-to-noise ratio, faster kinetics and greater response (Hires). It is also stably expressed for months at a time, suggesting its future application in the learning process and how this can reshape patterns in brain activity (Tian).
Calcium imaging
Calcium imaging is a scientific technique usually carried out in research which is designed to show the calcium status of a tissue or medium....
, or GECI. GECIs are designed to show the calcium ion status of a tissue or medium and are either transfected into cell lines or via transgenic crosses. GCaMP is created from a fusion 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), calmodulin
Calmodulin
Calmodulin is a calcium-binding protein expressed in all eukaryotic cells...
, and M13
M13
M13 may refer to:* M13 road , a metropolitan road in Durban, South Africa* M-13 , a state highway* M13 bacteriophage, a virus that infects bacteria* M13 link, a machine guns ammunition link...
(Hires).
GFP is circularly permuted so that the N- and C-termini are fused, creating a new terminus in the middle of the protein. Fused to the new terminus is calmodulin (CaM) and the M13 domain of a myosin light chain kinase (Nakai). Calmodulin is a symmetrical, hinge-like protein that binds to four calcium ions via E-F motifs. When calcium is present, CaM undergoes a conformational change, and the hinge region is able to bind helical peptide chains on target proteins, such as M13. When calcium is not present, there is a hole from the outside of the barrel into the chromophore
Chromophore
A chromophore is the part of a molecule responsible for its color. The color arises when a molecule absorbs certain wavelengths of visible light and transmits or reflects others. The chromophore is a region in the molecule where the energy difference between two different molecular orbitals falls...
, and GFP fluoresces dimly. However when calcium is present, the hole is plugged and GFP fluorescence increases (Hires). Therefore, GCaMP provides imaging of cellular processes, such as action potentials.
Due to its modularity, modifications in the different components of GCaMP have been made to achieve imaging that is brighter, faster, and has better signal-to-noise detection (Hires). Previous research has shown that amino acid substitutions in GFP could enhance folding activity and therefore increase fluorescence. These adaptations are seen in derivatives of GCaMP, such as GCaMP2 and GCaMP3. This “superfolder GFP” has also been utilized in GCaMP-HS to create improvements in brightness and signal amplitude (Muto). Since GFP has been modified, it is also probable that modifications could be made in calmodulin and its target proteins. However, this hypothesis has yet to be proven.
This imaging technique enables monitoring of neurons via action potentials, which would otherwise require large amounts of electrodes or electro-imaging. GCaMP3 has experimentally shown to have high signal-to-noise ratio, faster kinetics and greater response (Hires). It is also stably expressed for months at a time, suggesting its future application in the learning process and how this can reshape patterns in brain activity (Tian).