Ion channels in the nuclear envelope

CELL nuclei are capable of partitioning a wide variety of molecules from the cytosol, including macromolecules such as proteins1-11 and RNA12-14, and smaller peptides9,14-16, amino acids17, sugars18,19 and Na+ and K+ ions20,21, all of which can be accumulated in or excluded from the nuclear domain. There are two mechanisms behind this compartmentalization: selective retention of freely diffusible molecules, and selective entry through the nuclear envelope. It is generally accepted that the nuclear envelope restricts only the larger molecules22-24. Here we apply the patch-clamp technique to isolated murine pronuclei25 and show that the nuclear envelope contains K+-selective channels which have multiple conductance states, the maximal conductance being 200 pS. These channels, which contribute to the nuclear membrane potential26, may be important in balancing the charge carried by the movement of macromolecules in and out of the nucleus.