The enzyme, sphingomyelinase D (SMase D), splits a lipid called
sphingomyelin that surrounds the channel embedded in the cell
membrane. As a result, the channel opens to allow the passage of
small ions into and out of the cell, thereby generating
electrical currents. The new study, published online earlier
this month in the journal Nature, describes how SMase D opens
one type of ion channel called a voltage-gated potassium channel
(from brain, but experimentally expressed in the membrane of an
oocyte, or egg cell) without changing the membrane voltage. The
finding introduces a new paradigm for understanding the gating
of ion channels and lays the conceptual groundwork for designing
new drugs to control ion-channel activity in medical
intervention. Voltage-gated ion channels are embedded in the
cell membranes of most types of cells. It has been known for
over half a century that the channels open and close in response
to changes in electric voltage across the cell membrane, hence
their name. In some the cells,