Leanne L. Cribbs, Ph.D.
Associate
Professor of Medicine
and Physiology
Voltage activated Ca2+
channels are important for regulated entry of calcium into many
different cell types, which is essential for vital processes such as
muscle contraction, neurotransmitter release and pacemaker activity. Of
the five major classes of Ca2+ channel channels, two are most
prevalent in the cardiovascular system: high voltage-activated (HVA)
L-type, and low voltage-activated (LVA) T-type channels. Dr. Cribbs and
co-workers cloned three separate genes belonging to the novel T-type Ca2+
channel gene family, a 1G, a 1H and a 1I (see Selected Papers). Both a
1G and a 1H are present in the cardiovascular system, whereas a 1I is
found predominantly in brain.
The primary focus of Dr. Cribbs’
laboratory is to define the function of T-type Ca2+ channels
in the cardiovascular system in both normal and disease states. Although
LVA Ca2+ currents were first measured in cardiac cells in the
early 1980’s, little is known about their functional roles. This is
partially due to a lack of specific blockers for T-type channels, and
low sequence similarity with the well-studied L-type Ca2+
channels (the first to be cloned) made them difficult to clone by
homology-based screening methods. Now that multiple T-channel isotypes,
have been cloned, they can be used as tools to investigate their
relative distribution and functions.
Ongoing projects:
Immunolocalization of T-type Ca2+
channels.
We have generated antibodies against
a
1G and a 1H, and are currently using them
for immunolocalization studies to confirm their presence in heart and
vascular smooth muscle (see Figure). These studies provide information
about T-type channel localization that previously relied on
electrophysiological measurements; at the same time, we are developing
reagents useful for future studies of these channels at the protein
level.
Structure and function of cloned
ion channels are conveniently studied by transfecting into mammalian
cells in culture. T-type Ca2+ channel cDNA clones, when
expressed in HEK 293 cells, have many of the properties of the channels
expressed in native tissues. In order to study and manipulate the cloned
channels in native cardiac and VSM cell backgrounds, we have constructed
recombinant adenoviruses with a 1G and a 1H sequences. This approach
provides insight into molecular mechanisms of calcium regulation
involving LVA channels in a variety of different cell backgrounds.
Adenoviral vectors may also be useful for future studies in live animals
that could lead to potential gene therapy applications.
Structure-function of T-type Ca2+
channels
In collaboration with Dr. Jonathan
Satin (University of Kentucky), we are investigating structure-function
aspects of permeation and gating of T-type Ca2+ channels.
These studies combine molecular biology and electrophysiology to
identify molecular components of these complex channel functions, as
well as to explore different aspects of T-type channel regulation.
View a partial list of
Dr. Cribbs' publications through the National Library of
Medicine's PubMed online database.
