  In recent years it is increasingly being recognized that biochemical signals
are not necessarily constant in time and that the temporal dynamics of a signal
can be the information carrier. Moreover, it is now well established that
components are often shared between signaling pathways. Here we show by
mathematical modeling that living cells can multiplex a constant and an
oscillatory signal: they can transmit these two signals through the same
signaling pathway simultaneously, and yet respond to them specifically and
reliably. We find that information transmission is reduced not only by noise
arising from the intrinsic stochasticity of biochemical reactions, but also by
crosstalk between the different channels. Yet, under biologically relevant
conditions more than 2 bits of information can be transmitted per channel, even
when the two signals are transmitted simultaneously. These observations suggest
that oscillatory signals are ideal for multiplexing signals.
