Biomedical Summer Undergraduate Research Experience Program
(B-SURE)
The University of Texas Health Science Center at San Antonio (UTHSCSA)
SHAPIRO,
Mark S. (Physiology): The Shapiro lab focuses
on the physiology and regulation of neuronal ion channels. The patch-clamp
technique allows us to electrically record ionic currents from individual
living cells, or even from individual ion channel molecules, and these
minute signals are then studied using computers. Many signaling pathways
modulate ion channels as a way of regulating cellular excitability.
A vast system of neurotransmitters and hormones regulates cellular physiology
by acting on specific receptors in the cell membrane. The intracellular
actions of these receptors are often mediated by a ubiquitous family of
signal-transducing proteins called G proteins, biological molecular switches
that transduce the extracellular presence of a neurotransmitter into the
modulation of some intracellular target. These G protein-mediated
signaling pathways frequently act on ion channels. Our laboratory
studies the G-protein signaling pathways acting on an important neuronal
K+ current called the M current, called such because it is strongly
modulated by muscarinic acetylcholine receptors. We also study other
signals that act on the M current via protein kinases, especially tyrosine
kinases of the Src family. Functionally, modulation of the M current
plays a strong role in regulating the overall excitability of the neuron,
and on the release of neurotransmitter at nerve terminals.
Recently, the
molecular correlate underlying the M current was identified as members
of the KCNQ family of K+ channel genes. With these K+
channel clones, our lab has reconstituted modulation of the M current in
a heterologous mammalian expression system. With this reconstituted,
cloned system, as well as preparations of primary sympathetic neurons,
this lab uses the biophysical technique of the patch clamp, along with
techniques of molecular biology and biochemistry, to probe the molecular
mechanism of G-protein and tyrosine kinase modulation of the M current.
Intracellular Ca2+ ions also play a role in modulation of the
channels, and we use the technique of Ca2+ imaging that uses
fluorescent probes and very sensitive cameras to directly observe intracellular
Ca2+ in individual cells to determine how Ca2+ and
other putative second messengers interact with the channels to regulate
neuronal electrical signaling. With the combined use of biophysics,
molecular biology. biochemistry and Ca2+ imaging, this lab works
toward the identification of the relevant intracellular signaling molecules
in modulation of ion channels such as the M current/KCNQ channel and the
understanding of the precise mechanisms they use.
Mark
S. Shapiro's Web Page.
Modulation of potassium and calcium
channels in SCG neurons.