Genetically encoded red fluorescent voltage sensors enabling millivolt-resolution and high-speed neural voltage imaging
Voltage reporter molecules and compositions, and methods for detecting voltage and voltage change in cells are provided. Also provided are methods for delivery, expression, and use of the voltage reporter molecules in cells, tissues, and subjects.
1. A voltage reporter polypeptide, comprising an amino acid sequence set forth as SEQ ID NO: 1 or a functional variant thereof, wherein the functional variant has at least 97% amino acid sequence identity to SEQ ID NO: 1 and the amino acid sequence of the functional variant is not a sequence set forth as SEQ ID NO: 8, 9, 10, 11, 12, or 13, and wherein the functional variant comprises one or more amino acid substitutions, deletions, and insertions to the amino acid sequence set forth as SEQ ID NO: 1.
2. The voltage reporter polypeptide of claim, wherein the functional variant has at least 98%, 99%, or 100% amino acid sequence identity to the corresponding region of SEQ ID NO: 1.
3. The voltage reporter polypeptide of claim 1 , wherein the functional variant comprises the amino acid sequence of SEQ ID NO: 1 having one or more modifications, wherein the SEQ ID NO: 1 amino acid sequence is not modified at 1 or more of SEQ ID NO: 1 amino acid positions: 20, 41, 44, 60, 80, 88, 96, 107, 137, 162, 184, 199, and 242.
4. The voltage reporter polypeptide of claim 1 , wherein the functional variant comprises the amino acid sequence of SEQ ID NO: 1 having one or more modifications, wherein the amino acid sequence of SEQ ID NO: 1 is not modified at 1 or more of SEQ ID NO: 1 amino acid positions: 97, 129, 133, 149, 152, 153, 156, 193, 196, 197, 200, 223, and 227.
5. The voltage reporter polypeptide of claim 1 , wherein the amino acid sequence of the functional variant comprises the amino acid sequence set forth as SEQ ID NO: 2; SEQ ID NO: 3; SEQ ID NO: 4; SEQ ID NO: 5; SEQ ID NO: 6; or SEQ ID NO: 7.
6. A membrane comprising the voltage reporter polypeptide of claim 1 .
7. A fusion protein comprising the voltage reporter polypeptide of claim 1 .
8. A method of determining voltage in a cell, the method comprising,
a) monitoring a detectable signal of a voltage reporter polypeptide comprising an amino acid sequence set forth as SEQ ID NO: 1 or a functional variant thereof, wherein the functional variant has at least 97% amino acid sequence identity to SEQ ID NO: 1 and the amino acid sequence of the functional variant is not a sequence set forth as SEQ ID NO: 8, 9, 10, 11, 12, or 13, and wherein the functional variant comprises one or more amino acid substitutions, deletions, and insertions to the amino acid sequence set forth as SEQ ID NO: 1 expressed in a cell; and
b) determining a voltage characteristic in the cell by detecting a detectable signal of the reporter molecule of the expressed voltage reporter polypeptide, where the detectable signal indicates a voltage characteristic in the cell.
9. A method of identifying an effect of a test agent on a voltage in a cell, the method comprising,
(a) contacting a first cell comprising the voltage reporter polypeptide comprising an amino acid sequence set forth as SEQ ID NO: 1 or a functional variant thereof, wherein the functional variant has at least 97% amino acid sequence identity to SEQ ID NO: 1 and the amino acid sequence of the functional variant is not a sequence set forth as SEQ ID NO: 8, 9, 10, 11, 12, or 13, and wherein the functional variant comprises one or more amino acid substitutions, deletions, and insertions to the amino acid sequence set forth as SEQ ID NO: 1 expressed in a membrane of the first cell, with a stimulus that results in voltage in the cell that is detectable by the voltage reporter polypeptide;
(b) contacting the first cell or a cell in communication with the first cell with a test agent;
(c) detecting at least one voltage characteristic in the first cell, by detecting a detectable signal of the reporter molecule of the expressed voltage reporter polypeptide, where the detectable signal indicates voltage in the first cell; and
(d) comparing the at least one voltage characteristic detected in step (c) to the at least one voltage characteristic detected in a control cell, wherein a difference in the at least one voltage characteristic detected in the first cell compared to the at least one voltage detected in the control cell identifies an effect of the test agent on the voltage in the first cell.
10. A composition comprising one or more of a: voltage reporter polypeptide of claim 1 , a fusion protein comprising the voltage reporter.
11. The composition of claim 10 , further comprising one or more of: a carrier agent, a delivery agent, and a detectable agent.
12. The composition of claim 10 , wherein the composition is a pharmaceutically acceptable composition.
13. A cell comprising the voltage reporter polypeptide of claim 1 .
14. The cell of claim 13 , wherein the cell is a vertebrate cell, and optionally, is a mammalian cell.
15. A cell comprising the fusion protein of claim 7 .