Cells Highly Sensitive to Clostridial Neurotoxin

A method for making a population of cells that are highly sensitive to clostridial neurotoxin, the method comprising:

• (a) contacting recombinant cells that express an indicator protein with clostridial neurotoxin;
• and
• (b) thereafter, selecting the cells that exhibit cleavage of the indicator protein.

The method of any one of the preceding claims, wherein step (a) involves culturing the cells in media comprising clostridial neurotoxin at a concentration of from about 0.0001 to about 10,000 pM.

The method of any one of the preceding claims, wherein step (a) involves culturing the cells in media comprising clostridial neurotoxin for about 2 hours or more.

The method of any one of the preceding claims, wherein the indicator protein comprises a SNARE domain.

The method of any one of the preceding claims, wherein the indicator protein comprises the amino acid sequence of (i) syntaxin, (ii) synaptobrevin, (iii) SNAP-25, or (iv) a variant or fragment thereof that is susceptible to proteolysis by the protease component of a wild-type clostridial neurotoxin;

• preferably SNAP-25.

The method of any one of the preceding claims, wherein the indicator protein is labelled;

• preferably labelled with the amino acid sequence of one or more fluorescent protein label.

The method of any one of the preceding claims, wherein the indicator protein comprises a C-terminal label;

• preferably an N-terminal label and a C-terminal label;
• preferably wherein the N-terminal label and a C-terminal label are distinguishable.

The method of any one of the preceding claims, wherein the indicator protein comprises the amino acid sequence of (i) SNAP-25, or a variant or fragment thereof, (ii) an N-terminal label, and (iii) a C-terminal label.

The method of any one of the preceding claims, wherein the indicator protein is labelled with the amino acid sequence of mScarlet and the amino acid sequence of NeonGreen.

The method of any one of the preceding claims, wherein the indicator protein is labelled with the amino acid sequence of mScarlet as an N-terminal label and NeonGreen as a C-terminal label.

The method of any one of the preceding claims, wherein the cells have been genetically engineered to express (or overexpress) the indicator protein.

The method of any one of the preceding claims, wherein the population of cells or recombinant cell (e.g. of step a)) is produced by introducing into a cell a nucleic acid encoding the indicator protein.

The method of any one of the preceding claims, wherein the method further comprises introducing into the recombinant cell or the population of cells (e.g. of step a) a nucleic acid encoding an indicator protein.

The method of any one of the preceding claims, wherein the indicator protein is not cleaved in the absence of the clostridial neurotoxin, or a proteolytically active domain thereof.

The method of any one of the preceding claims, wherein the indicator protein is not readily degraded in the cell but, following cleavage thereof, one of the resulting fragments (preferably the C-terminal fragment) is.

The method of any one of the preceding claims, wherein the indicator protein comprises a C-terminal label and the C-terminal label is not released from (e.g. cleaved off) the indicator protein in the absence of the clostridial neurotoxin, or a proteolytically active domain thereof.

The method of any one of the preceding claims, wherein the indicator protein comprises a C-terminal label and the full-length indicator protein is not readily degraded in the cell but, following cleavage thereof, the resulting C-terminal fragment is and the degradation of the C-terminal fragment results in the degradation of the C-terminal label.

The method of any one of the preceding claims, wherein the indicator protein comprises a C-terminal label and the full-length indicator protein is not readily degraded in the cell but, following cleavage thereof, the resulting C-terminal fragment is and the degradation of the C-terminal fragment results in the degradation of the C-terminal label and cleavage of the indicator protein is determined by measuring the signal from the C-terminal label following the contacting of the cell(s) with clostridial neurotoxin;

• preferably wherein a decrease of the C-terminal label during or post-contact with the clostridial neurotoxin (e.g. during or post-step a)) is indicative of cleavage of the indicator protein;
• more preferably wherein a decrease of the C-terminal label during or post-contact with the clostridial neurotoxin (e.g. during or post-step a)) confirms cleavage of the indicator protein.

The method of any one of the preceding claims wherein, following the contact, the cell is lysed and the resulting cell lysate is contacted with antibodies and a Western blot performed.

The method of any one of the preceding claims, wherein the cells of step a) comprise an exogenous nucleic acid encoding a receptor having binding affinity for the clostridial neurotoxin and/or an exogenous nucleic acid providing for expression of a ganglioside having binding affinity for the clostridial neurotoxin;

• preferably an exogenous nucleic acid encoding said receptor and an exogenous nucleic acid providing for expression of said ganglioside.

The method of any one of the preceding claims, wherein the method comprises, prior to the first contacting step (e.g. step a)), introducing into the cells an exogenous nucleic acid encoding:

• a clostridial neurotoxin receptor, or a variant or fragment thereof that has the ability to bind clostridial neurotoxin;
• and/or an enzyme of the ganglioside synthesis pathway, or a variant or fragment thereof that has the catalytic activity of such enzyme.

The method of any one of the preceding claims, wherein the cells of step a) comprise an exogenous nucleic acid encoding an enzyme of the ganglioside synthesis pathway (or a variant or fragment thereof that has the catalytic activity of such an enzyme).

The method of any one of the preceding claims, wherein the cells of step a) comprise an exogenous nucleic acid encoding glucosylceramide synthase, GalT-I, GalNAcT, GM3 synthase, GD3 synthase, GT3 synthase, galactosylceramide synthase, GM4 synthase, GalT-II, ST-IV, or ST-V, or a variant or fragment thereof that has the catalytic activity of such an enzyme;

• preferably GD3 synthase, or a variant or fragment thereof that has the catalytic activity of GD3 synthase;
• more preferably GD3 synthase.

The method of any one of the preceding claims, wherein the cells (e.g. of step a)) express more of the receptor and/or ganglioside (for example, via an enzyme of the ganglioside synthesis pathway, or a variant or fragment thereof that has the catalytic activity of such an enzyme) when compared with a cell lacking said nucleic acid (preferably lacking said exogenous nucleic acid).

The method of any one of the preceding claims, wherein the cell has been genetically engineered to express or overexpress a protein receptor, or a variant or fragment thereof that has the ability to bind clostridial neurotoxin.

The method of any one of the preceding claims, wherein the receptor is SV2 or a synaptotagmin (or a variant or fragment thereof that has the ability to bind clostridial neurotoxin).

The method of any one of the preceding claims, wherein the receptor is SV2 (or a variant or fragment thereof that has the ability to bind clostridial neurotoxin).

The method of any one of the preceding claims, wherein the receptor is SV2A or SV2C, preferably SV2A (or a variant or fragment thereof that has the ability to bind clostridial neurotoxin).

The method of any one of the preceding claims, wherein the receptor is the fourth luminal domain of SV2A or SV2C.

The method of any one of the preceding claims, wherein the nucleic acid (preferably exogenous nucleic acid) is introduced by transfection.

The method of any one of the preceding claims, wherein the recombinant cell is produced by genetically engineering a cell to express:

• (i) a clostridial neurotoxin receptor, or a variant or fragment thereof that has the ability to bind clostridial neurotoxin;
• and/or (ii) an enzyme of the ganglioside synthesis pathway, or a variant or fragment thereof that has the catalytic activity of such enzyme.

The method of any one of the preceding claims, wherein the cells selected or isolated are those in which 20% or more of the indicator protein present in the cell has been converted into cleavage products.

The method of any one of the preceding claims, wherein, with each iteration of step (a), the cells are contacted with less clostridial neurotoxin than they were contacted with during the previous iteration of step (a).

The method of any one of the preceding claims, wherein the cells (e.g. of step a) are neuronal cells, non-neuronal cells, neuroendocrine cells, embryonic kidney cells, breast cancer cells, neuroblastoma cells, or neuroblastoma-glioma hybrid cells;

• preferably non-neuronal cells.

The method of any one of the preceding claims, wherein the cells (e.g. of step a) are neuroblastoma cells or neuroblastoma-glioma cells.

The method of any one of the preceding claims, wherein the cells (e.g. of step a) are neuroblastoma-glioma cells.

The method of any one of the preceding claims, wherein the cells (e.g. of step a) are NG108 cells.

The method of any one of the preceding claims, wherein the ganglioside is selected from GM1a, GD1a, GD1b, GT1b, and GQ1b;

• preferably wherein the cells (e.g. of step a) have been genetically engineered to express or overexpress GM1a, GD1a, GD1b, GT1b, and/or GQ1b.

The method of any one of the preceding claims, wherein the ganglioside is selected from GD1a, GD1b, and GT1b;

• preferably wherein the cells (e.g. of step a)) have been genetically engineered to express or overexpress GD1a, GD1b, and/or GT1b.

The method of any one of the preceding claims, wherein the ganglioside is selected from GD1b and GT1b;

• preferably wherein the cells (e.g. of step a)) have been genetically engineered to express or overexpress GD1b and/or GT1b.

The method of any one of the preceding claims, wherein the clostridial neurotoxin is a botulinum neurotoxin.

The method of any one of the preceding claims, wherein the clostridial neurotoxin is selected from BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F, BoNT/G, and BoNT/H.

The method of any one of the preceding claims, wherein the clostridial neurotoxin is BoNT/A.

The method of any one of the preceding claims, wherein in step a) (e.g. contacting a population of cells with a clostridial neurotoxin, or contacting recombinant cells that express an indicator protein with clostridial neurotoxin) the clostridial neurotoxin is present at a concentration of about 0.0001 to about 100,000 pM, about 0.0001 to about 50,000 pM, about 0.0001 to about 20,000 pM, 0.0001 to about 10,000 pM, about 0.0001 to about 1,000 pM, about 0.0001 to about 500 pM, about 0.0001 to about 300 pM, about 0.0001 to about 100 pM, about 0.0001 to about 10 pM, or about 0.0001 to about 1 pM.