November 6, 2001
Link to Our Ancient Past Is Confirmed
in Research On Brain's Potassium Channels
Penn Scientists Match 'Molecular Gates' in Mammals
and Primitive Bacterial Animals
Research
on components of the brain's electrical signaling system
has answered a basic question about our human evolution,
confirming scientific belief that we two-legged, computer-using
creatures are descended from prokaryotes -- cellular
organisms so primitive and simple that they exist without
nuclei or cell walls.
The study, led by Zhe Lu, MD, PhD, an Associate
Professor in the Department of Physiology at
the University of Pennsylvania School of Medicine have
been recently published in the journal Nature.
The research by Lu and his colleagues focused on the
structure and function of molecules called potassium
channels, which are essential to how the brain works.
When potassium channels open and close, they control
the flow of potassium ions across cell membranes. The
current contributes to the electrical signals in nerve,
muscle and endocrine cells.
Scientists who study the brain's electrical signals
have relied on a blue-print developed from functional
studies of eukaryotic (neuronal) potassium channels
and structural studies of prokaryotic (bacterial) potassium
channels, based on the assumption that the two channels
are essentially the same. However this assumption has
recently been challenged.
Lu and his collaborators devised a project in which
the pore of a prokaryote's potassium channel (the interior
core of the channel) was substituted for the pore of
a potassium channel in a euokaryote. The scientists
found that the eukarotic channel continued to function
essentially as it had previous to the substitution.
"This has very profound implications for evolution,"
Lu said. "It appears the potassium channels in
advanced brains and hearts of mammals have evolved from
something like this bacterial channel. So what we learn
from the more easily studied bacterial channels can
be directly applied to our understanding of potassium
channels such as those in our brains."
In the study, Lu worked with Penn colleagues, Angela
Klem, research specialist, and Yajamana Ramu,
PhD.
The work was funded by the National Institutes of Health.
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The University of Pennsylvania Health System is distinguished
not only by its historical significance -- first hospital
(1751), first medical school (1765), first university
teaching hospital (1874), first fully integrated academic
health system (1993) -- but by its leadership in the
practice of medicine in the 21st Century. Among all
American medical schools, Penn ranks second in funding
from the National Institutes of Health, perhaps the
single most important barometer of research strength.
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