CatCh Mutant Channelrhodopsin 2 Light Sensitivity Kinetics
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current light-gated cation channels, such as wild-type Channelrhodopsin-2 (ChR2), have limitations in light sensitivity and response kinetics, which hinder their application in activating neurons distant from the light source and pose risks of cell damage due to high blue light intensities required for activation, and slow kinetics of mutants like C128 and D156 variants.
Innovation Solution
Development of a mutant channelrhodopsin, designated as CatCh, with enhanced Ca++ permeability, which increases inner membrane surface potential through high light-gated Ca++ influx, activating voltage-gated Na+ channels and BK channels, thereby improving light sensitivity and response kinetics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If wild-type Channelrhodopsin-2 (ChR2) is used, then the channel can be activated by light, but the light sensitivity is insufficient requiring high blue light intensities that risk cell damage
Solution Approach 1:
The patent applies parameter changes by mutating specific amino acid residues (C128 and D156) in the ChR2 protein structure. These mutations alter the channel's physical and chemical parameters, specifically increasing its light sensitivity and modifying ion permeability properties, thereby achieving the desired improvement in light sensitivity while reducing the harmful effects of high light intensity exposure
Solution Approach 2:
The invention creates a composite functional channel by combining ChR2 with calcium-permeable channel properties through mutation. The resulting CatCh channel integrates the light-gating function of ChR2 with enhanced calcium permeability, creating a hybrid functional unit that achieves both high light sensitivity and controlled ion selectivity
2Illumination intensity
If mutations at positions C128 and D156 are introduced to increase light sensitivity, then light sensitivity improves significantly, but channel kinetics become markedly slowed with open lifetimes up to 30 minutes
Solution Approach 1:
The patent applies local quality by making a specific localized mutation at position L132 in helix 3, while keeping other regions of the protein unchanged. This localized modification selectively alters the calcium permeability and gating properties of the channel without affecting the overall structural integrity or the light-sensing mechanism, thereby achieving improved calcium influx while maintaining faster kinetics compared to the C128/D156 mutants
Solution Approach 2:
The invention uses partial action by introducing only a single point mutation (L132C) rather than multiple mutations. This minimal modification is sufficient to achieve the desired enhancement in calcium permeability and light sensitivity while avoiding the excessive structural changes that would lead to markedly slowed kinetics
3Productivity
If high blue light intensities are used to activate ChR2, then sufficient neuronal activation is achieved, but cell damage risk increases
Solution Approach 1:
The mutation at L132 changes the channel's parameter for calcium permeability and light sensitivity, enabling the channel to achieve sufficient neuronal activation at lower light intensities. This parameter modification directly addresses the contradiction by allowing effective neuronal activation without requiring high blue light intensities that would cause cell damage
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
CatCh exhibits a four-fold higher Ca++ permeability, 70-fold higher light sensitivity, and faster response kinetics compared to WT ChR2, enabling precise and fast action potentials with lower light intensities, suitable for clinical and research applications, including visual restoration and cancer cell ablation.
Implementation Method 1
The light-gated, inwardly rectifying cation channel, channelrhodopsin-2 (ChR2) has become a preferred tool for the targeted light-activation of neurons
Implementation Method 2
CatCh has a four-fold higher Ca ++ permeability than WT ChR2
Implementation Method 3
Since it is known that a cell's inner membrane surface potential is strongly influenced by Ca ++via Ca ++Ca lcium t ranslocating Ch annelrhodopsin
Data Source
Figure 1
Figure 2a~2b
Figure 2c~2d
AI summary
The invention relates to mutant channelrhodopsins having improved properties, nucleic acid constructs encoding same, expression vectors carrying the nucleic acid construct, cells comprising said nucleic acid construct or expression vector, and their respective uses.