at the Picower Institute for Learning and Memory at the Massechusetts Institute
of Technology (MIT) have found that a well-known protein, called septins, may
have an unexpected role in the brain and may lead to potential new treatments
for diseases such as Alzheimer''s and Parkinson''s.
study by Morgan H. Sheng, Menicon Professor of Neuroscience and a Howard Hughes
Medical Institute investigator, and colleagues to be published in the October
23 issue of Current Biology shows that the same protein that enables a yeast cell
to bud into two daughter cells also helps neurons sprout the branch-like protrusions
used to communicate with other neurons.
are a type of proteins known since the 1970s to play an essential function in
the process through which the cytoplasm of a single yeast cell divides. "In
yeast, septin is localised exactly at the neck between the yeast mother cell and
the bud or emerging daughter cell," Sheng said. "Amazingly, we found
septin protein localised at the base of the neck of neuronal dendritic spines
and at the branchpoint of dendritic branches."
of the 14 septins found in mammals are found in the brain. One of them, Sept7,
appears the most, but its role was unclear. Septins form long filaments and act
as scaffolds, recruiting other proteins into their assigned roles of builders
of the cell infrastructure.
neurons don''t divide, they form protrusions that eventually elongate into dendritic
branches. Dendrites conduct electrical stimulation from other neurons to the cell
body of the neuron from which the dendrites project.
stimulation is transmitted via synapses, which are located at various points along
the dendritic branches. Dendrites play a critical role in receiving these synaptic
inputs. "Because dendritic spines are important for synaptic function and
memory formation, understanding of septins may help to prevent the loss of spines
and synapses that accompanies many neurodegenerative diseases," said co-author
Tomoko Tada, a post-doctoral associate in the Picower Institute. "Septin
could be a potential target protein to treat these diseases," he added.
have found that septin was essential for normal branching and spine formation.
An abundance of septin made dendrites grow and proliferate while a dearth of septin
made them small and malformed.
septin expression and function would enhance the stability of spines and synapses,
and therefore be good for cognitive functions such as learning and memory,"
Sheng said. His laboratory is now exploring ways to prevent septin degradation
work has also been supported by the National Institutes of Health and the RIKEN-MIT
Neuroscience Research Center.