Abstract: A method of identifying a compound that modulates NCKX-mediated calcium ion exchange across a cell membrane, the method comprising the steps of providing an adherent cell, the cell membrane of which comprises a NCKX polypeptide or a functionally equivalent variant thereof, exposing the cell in suspension to a fluorescent calcium-sensitive dye, thereby causing intracellular uptake of the dye, settling the cell onto a solid support without allowing the cell to adhere to the solid support, exposing the cell to a test compound, exposing the cell to calcium and potassium ions, and measuring fluorescence from the intracellular calcium-sensitive dye after exposure of the cell to the test compound and the calcium and potassium ions, thereby to determine the rate and/or amount of calcium ion exchange across the cell membrane in the presence of the test compound.

Abstract: The invention provides a method of identifying compounds that either increase or decrease skin and/or hair pigmentation, the method comprising determining the ability of a test compound to modulate NCKX-mediated calcium ion movement across a membrane (e.g. NCKX5). The method may comprise the steps of exposing a membrane comprising a NCKX molecule or variant, fusion or derivative thereof to a test compound and measuring either directly or indirectly the calcium ion concentration on one or both sides of the membrane. The invention also relates to kits, nucleic acid molecules, polypeptides and cells useful in the method of the invention.