The protein, called kibra, was linked in previous studies in humans to memory and protection against late-onset Alzheimer’s disease. The new work in mice, reported in the Sept. 22 issue of Neuron, shows that kibra is an essential part of a complex of proteins that control the sculpting of brain circuitry, a process that encodes memory.
“There are populations of humans who are slightly smarter and have better memory recall than others, and these traits have been mapped to the gene that codes for the kibra protein” says Richard L. Huganir, Ph.D., professor and director of the Solomon H. Snyder Department of Neuroscience at the Johns Hopkins University School of Medicine, and a Howard Hughes Medical Institute investigator. “Our studies in mice show that this same gene is involved in the operation of synapses, through which neurons communicate, and in brain plasticity, suggesting that’s what its role might be in humans too.”
In their lab, Huganir and neuroscience graduate student Lauren Makuch isolated kibra from mouse brain cells and confirmed by standard biochemical tests that it interacted with a neurotransmitter receptor in the brain known as the AMPA receptor.
They then determined that kibra regulated the delivery of AMPA receptors from inside the brain’s nerve cells out to the synapses by first growing live brain cells from embryonic mice in a dish for two weeks and then genetically altering some of those cells to produce less kibra protein. Next, they placed the live neurons in an imaging chamber and recorded the activity of the AMPA receptors once a minute for 60 minutes. Results showed that AMPA receptors moved faster in the cells with less kibra than in control cells with normal amounts of the protein demonstrating that kibra regulates how receptors are delivered to the surface of brain cells.
The work affirms that the addition of AMPA receptors to synapses serves to strengthen connections in the brain, Huganir says, noting that most forms of learning involve the strengthening of some synapses and the weakening of others, a phenomenon known as plasticity, which is responsible for sculpting circuits in the brain that encode memory. Without kibra, this process doesn’t function properly; as a result, learning and memory are compromised. Huganir hypothesizes that kibra specifically helps create a pool of receptors that is used to add receptors to synapses during learning.
Later in their study, using slices of brain from mice with or without kibra, postdoctoral fellow Lenora Volk recorded and measured electrical activity and synaptic plasticity in nerve cells, noting that mice lacking kibra showed less plasticity, a phenomenon that translates into a reduced ability to learn and recall new information, Makuch explains.
Finally, the Hopkins researchers conducted a series of behavioral studies using adult mice to compare the learning and memory of normal mice with those that made much less kibra protein. They used a well-established fear-conditioning task by placing the mice in a training chamber and exposing them to a tone and subsequent shock. After two days of training, the animals’ rates of “freezing” in place — a normal rodent response to fear — were measured. Kibra-deficient mice took longer to learn to associate the tone with the shock than it did the others. On day three of the experiment, upon simply being placed back into the training chamber, the normal mice had a high rate of freezing, while the kibra-deficient mice had a very low rate, indicating impairments in contextual fear response and therefore, memory.
“Our work in the mammalian brain shows that kibra, required for normal brain function and associated with learning and memory, is important for regulating the trafficking of AMPA receptors,” Huganir says. “In addition, as kibra has been associated with protection against early onset Alzheimer’s disease, these studies may help define novel therapeutic targets for the treatment of age-related memory disorders.”
This study was funded by the National Institutes of Health and the Howard Hughes Medical Institute.
Authors on the paper, in addition to Huganir, Makuch and Volk are Victor Anggono, Richard C. Johnson, and Yilin Yu, all of Johns Hopkins.
Other authors are Kerstin Duning and Joachim Kremerskothen, University Hospital Münster, Germany; Jun Xia, The Hong Kong University of Science and Technology, China; and Kogo Takamiya, University of Miyazaki, Japan.On the Web:
Maryalice Yakutchik | Newswise Science News
Climate Impact Research in Hannover: Small Plants against Large Waves
17.08.2018 | Leibniz Universität Hannover
First transcription atlas of all wheat genes expands prospects for research and cultivation
17.08.2018 | Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung
New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference
Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...
Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.
Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...
17.08.2018 | Event News
08.08.2018 | Event News
27.07.2018 | Event News
17.08.2018 | Physics and Astronomy
17.08.2018 | Information Technology
17.08.2018 | Life Sciences