A microtubule 'roadway' in the retina helps provide energy for vision

A microtubule 'roadway' in the retina helps provide energy for vision
A microscopic image of bipolar cells, including their giant synaptic terminals, in a slice of goldfish retinal tissue. Credit: Graffe et al., 2015

Researchers have discovered a thick band of microtubules in certain neurons in the retina that they believe acts as a transport road for mitochondria that help provide energy required for visual processing. The findings appear in the July issue of The Journal of General Physiology.

The retina is a layer of tissue in the back of the eye that converts light into nerve impulses. The retina contains small, specialized neurons called that transmit information from light-sensitive photoreceptor cells to ganglion neurons, which send information to the brain for interpretation as images.

Bipolar cells are continuously active, a characteristic few other neurons share. They require a constant supply of to mediate the sustained release of the contents of an enormous number of , which store the transmitters that convey information between neurons. An intriguing new study of their subcellular structure could help explain how bipolar synaptic terminals meet such excessive energy demands.

Using cutting-edge 3D microscopy, researchers from the National Heart, Lung, and Blood Institute and Yale University examined the subcellular architecture of presynaptic terminals in retinal bipolar cells of live goldfish. Goldfish retinal bipolar cells have giant presynaptic terminals that make them especially amenable for investigation. Unexpectedly, the team discovered a thick band of microtubules, a component of the cell's cytoskeleton, that extended from the axon of the neuron into the synaptic terminal and then looped around the interior periphery of the terminal.

The microtubule band appeared to associate with —organelles known for providing energy to cells—in the synaptic terminal. When the researchers administered drugs to inhibit the movement of certain "motor" proteins that transport mitochondria and other cargo within the cell by traveling along , the mitochondria accumulated in the axon of the neuron and never made it to the synaptic terminal.

A microtubule 'roadway' in the retina helps provide energy for vision
Fluorescently labeled microtubules extend from the tips of the dendrites (top) into the axon and down into the giant synaptic terminal (bottom) of a single isolated goldfish retinal bipolar cell. A loop of microtubules encircles the inner plasma membrane of the terminal and anchors mitochondria. Credit: Graffe et al., 2015

The findings suggest that these previously unknown microtubule structures provide a "roadway" for the transport of mitochondria crucial to maintain energy supplies into the synaptic terminals of these highly active associated with vision.

More information: Graffe, M., et al. 2015. J. Gen. Physiol. DOI: 10.1085/jgp.201511396

Journal information: Journal of General Physiology

Citation: A microtubule 'roadway' in the retina helps provide energy for vision (2015, June 29) retrieved 24 March 2023 from https://medicalxpress.com/news/2015-06-microtubule-roadway-retina-energy-vision.html
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