Researchers at Umeå University have discovered a previously unknown cellular component, an organelle, inside the neurons we use to perceive smell. The discovery may have implications for further research into the impaired sense of smell, which is a common symptom of COVID-19.
A prerequisite to finding a treatment for impaired smell is to first understand how the sense of smell works.”
Staffan Bohm, Professor, Department of Molecular Biology, Umeå University
What the researchers have discovered is a so-called organelle inside nerve cells, which had not been observed before. Researchers have named the newly discovered organelle the multivesicular transducosome. The discovery was made possible by the unique microscopy infrastructure at Umeå University.
Organelles are different “work stations” within cells that can be compared to different organs in the body, meaning different organelles have different functions in the cell. Most organelles are common to different types of cells, but there are also organelles with specific functions that occur only in certain types of cells. Olfactory nerve cells have long projections, called cilia, that protrude into the nasal cavity and contain the proteins that bind odorous substances and thus initiate nerve impulses in the brain. The conversion of odor into nerve impulses is called transduction, and the recently discovered organelle contains only transduction proteins.
The role of the transductosome is to store and keep the transduction proteins separate from each other until they are needed. Upon olfactory stimulation, the outer membrane of the organelle breaks, releasing the transduction proteins so that they can reach the cilia of the neuron, and smell is perceived. The researchers also discovered that the transductosome carries a protein called retinitis pigmentosa 2, RP2, which is known to regulate transduction in the eye’s photoreceptor cells. If the RP2 gene is mutated, it can cause a variant of the eye disease retinitis pigmentosa that damages the light-sensitive cells in the eye.
“A question for further research is whether the transductosome plays a role in vision and whether it is present in brain neurons that are activated by neurotransmitters and not light and smell. If so, the discovery may prove even more significant “, says Staffan Bohm.
The transducosome was discovered when researcher Devendra Kumar Maurya used a new technique called correlative microscopy. The technique combines electron microscopy and confocal microscopy so that the internal structures of a cell and the location of different proteins can be seen simultaneously. Devendra’s development of the method was crucial to the discovery, allowing the technique to be used to analyze intact neurons in tissue sections.
The study is published in the scientific journal Nature Communications.
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Journal reference:
Maurya, DK, et al. (2023) A multivesicular body-like organelle mediates stimulus-regulated trafficking of olfactory ciliary transduction proteins. Communications of nature. doi.org/10.1038/s41467-022-34604-y.