Science / Technology
Autopilot Guides Proteins in Brain
- USC College molecular and computational biologist Don Arnold
- Photo/Dietmar Quistorf
By Carl Marziali on April 20, 2009 7:45 AM
Proteins go everywhere in the cell and do all sorts of work, but a fundamental question has eluded biologists: How do the proteins know where to go?
“There’s no little man sitting there, putting the protein in the right place,” said Don Arnold, a molecular and computational biologist at USC College.
“Proteins have to have in them encoded information that tells them where to go in the cell.”
In a study appearing online this week in Nature Neuroscience, Arnold and collaborators solve the mystery for key proteins in the brain.
Neurons have separate structures for receiving signals (dendrites) and for sending them (axons). The electrical properties of each depend on different proteins. But the proteins travel in bubbles, or vesicles, powered by motors known as kinesins that travel along tiny molecular paths.
Even though the paths point to both axons and dendrites, dendritic proteins end up in dendrites, and axonal proteins go to the axons. How?
Arnold’s group discovered a crude but effective sorting mechanism. At first, kinesins blindly carry both types of proteins towards the axon.
However, dendritic proteins enable the vesicles transporting them to bind to a second motor, known as myosin, that literally walks them back into the dendrite.
This filter ensures that only axonal proteins make it into the axon. The others are caught by the second motor and diverted to the dendrite.
“This mechanism fishes these things out of the axon,” Arnold said.
Once in the dendrite, the proteins either land in a place where they can do their electrical work or they move back towards the axon, only to be fished out again.
On its face, the process is inefficient, Arnold said, “but it is very effective.”
The discovery may enable finer control over neurons for basic research or for treatment of neurological disorders. Potentially, scientists could target only dendrites or axons in a neuron so as to study its outgoing or incoming impulses.
In addition to these potential applications, the study is notable for its contribution to the understanding of the brain and of protein transport in general.
“It’s a very basic question, something people have been wondering about for a long time,” Arnold said.
The co-authors on the study were first author Tommy Lewis, a graduate student in the molecular and computational biology graduate program at USC, as well as Tianyi Mao and Karel Svoboda from the Howard Hughes Medical Institute at the Janelia Farm Research Campus.
The National Institutes of Health and the Howard Hughes Medical Institute funded the research.
TAGS: research
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The Wall Street Journal highlighted the $200 million naming gift from USC Trustee and alumnus David Dornsife and wife Dana Dornsife to the USC Dornsife College, and the $110 million gift from USC Trustee and USC Viterbi School alumnus John Mork and wife Julie to create the USC Mork Family Scholars Program.
KPCC-FM reported that this fall USC will offer Persian language courses for the first time. A $250,000 grant from the Farhang Foundation helped to establish the program. Bruce Zuckerman of the USC Dornsife College said he has many students interested in the Persian language, culture and region. “The Iranian region is one that has great impact on our lives today and has had great impact going back into ancient times,” he said. The story noted that USC and the Farhang Foundation hope to raise more money to create an Iranian studies minor. Payvand also featured the new courses.
American Songwriter ran a Q&A with Christopher Sampson of the USC Thornton School about the school’s Popular Music program, which Sampson founded. He noted that the program has been available as a major in Songwriting since 2009, and has incorporated a diverse range of musical genres. “We have now established a consistent track record of students having professional success to know that the program gets results,” Sampson said. He also highlighted the achievements of Songwriting faculty members Lamont Dozier, Andrea Stolpe and David Poe of the Thornton School.
The Economist featured research by Valter Longo of the USC Davis School finding that short periods of fasting could help cancer patients better tolerate chemotherapy, and may even make treatment more effective. The Globe and Mail (Canada) reported that cancerous tumors are essentially energy hogs. “They need to burn lots of energy just to stay alive,” Longo said. The study was also covered by Irish Independent (Ireland), Magyar Tavirati Iroda (Hungary), Anadolu Ajansi (Turkey), Son Haber (Netherlands), Vietnam+ (Vietnam), Turkish Radio and Television (Turkey) and Romania Libera (Romania).
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