ScienceDaily (June 11, 2012) — In a pair of related studies, scientists from the Florida campus of The Scripps Research Institute have identified several proteins that help regulate cells’ response to light — and the development of night blindness, a rare disease that abolishes the ability to see in dim light.
In the new studies, published recently in the journals Proceedings of the National Academy of Sciences (PNAS) and The Journal of Cell Biology, Scripps Florida scientists were able to show that a family of proteins known as Regulator of G protein Signaling (RGS) proteins plays an essential role in vision in a dim-light environment.
“We were looking at the fundamental mechanisms that shape our light sensation,” said Kirill Martemyanov, a Scripps Research associate professor who led the studies. “In the process, we discovered a pair of molecules that are indispensible for our vision and possibly play critical roles in the brain.”
In the PNAS study, Martemyanov and his colleagues identified a pair of regulator proteins known as RGS7 and RGS11 that are present specifically in the main relay neurons of the retina called the ON-bipolar cells. “The ON-bipolar cells provide an essential link between the retinal light detectors — photoreceptors and the neurons that send visual information to the brain,” explained Martemyanov. “Stimulation with light excites these neurons by opening the channel that is normally kept shut by the G proteins in the dark. RGS7 and RGS11 facilitate the G protein inactivation, thus promoting the opening of the channel and allowing the ON-bipolar cells to transmit the light signal. It really takes a combined effort of two RGS proteins to help the light overcome the barrier for propagating the excitation that makes our dim vision possible.”
In the Journal of Cell Biology study, Martemyanov and his colleagues unraveled another key aspect of the RGS7/RGS11 regulatory response — they identified a previously unknown pair of orphan G protein-coupled receptors (GPCRs) that interact with these RGS proteins and dictate their biological function.
GPCRs are a large family of more than 700 proteins, which sit in the cell membrane and sense various molecules outside the cell, including odors, hormones, neurotransmitters, and light. After binding these molecules, GPCRs trigger the appropriate response inside the cell. However, for many GPCRs the activating molecules have not yet been identified and these are called “orphan” receptors.
The Martemyanov group has found that two orphan GPCRs — GPR158 and GPR179 — recruit RGS proteins and thus help serve as brakes for the conventional GPCR signaling rather than play an active signaling role.
In the case of retinal ON-bipolar cells, GPR179 is required for the correct localization of RGS7 and RGS11. Their mistargeting in animal models lacking GPR179 or human patients with mutations in the GPR179 gene may account for their night blindness, according to the new study. Intriguingly, in the brain GPR158 appears to play a similar role in localizing RGS proteins, but instead of contributing to vision, it helps RGS proteins regulate the m-opioid receptor, a GPCRs that mediates pleasurable and pain-killing effects of opioids.
“We are really in the very beginning of unraveling this new biology and understanding the role of discovered orphan GPR158/179 in regulation of neurotransmitter signaling in the brain and retina,” Martemyanov said. “The hope is that better understanding of these new molecules will lead to the design of better treatments for addictive disorders, pain, and blindness.”
In a groundbreaking study, researchers from the Czech Republic and the United Kingdom have discovered a link between the déjà vu phenomenon and structures in the human brain, effectively confirming the neurological origin of this phenomenon. Despite past studies investigating this phenomenon in healthy individuals, no concrete evidence had ever emerged … until now. The study is presented in the journal Cortex.
Led by the Central European Institute of Technology, Masaryk University (CEITEC MU) and Masaryk University’s Faculty of Medicine in the Czech Republic, researchers discovered that specific brain structures have a direct impact on the déjà vu experience. The findings of their study showed that the size of these structures are considerably smaller in the brains of the people experiencing déjà vu, compared with individuals who had no personal experience with déjà vu.
The team from CEITEC MU, along with colleagues from other Brno research institutions as well as the University of Exeter in the United Kingdom succeeded in providing huge insight into this phenomenon that has perplexed many over the years.
The team observed how small structures in the brain’s medial temporal lobes, in which memory and recollections originate, were considerably smaller in individuals with the occurrence of déjà vu than in individuals who have not experienced déjà vu. Their findings also showed that the more often the examined individuals experience déjà vu, the smaller the brain structures are.
“One hundred and thirteen healthy subjects underwent a structural examination of their brain by means of magnetic resonance and subsequently by using a new sensitive method for an automatic analysis of brain morphology (source-based morphometry) [and] the size of individual brain regions was compared among the individuals who have never experienced déjà vu and those who have experienced it,” said lead author Milan Brázdil from CEITEC.
“Except for the presence of the examined phenomenon, both groups of individuals were fully comparable. When we stimulate the hippocampus, we are able to induce déjà vu in neurological patients. By finding the structural differences in hippocampus in healthy individuals who do and do not experience déjà vu, we have unambiguously proved that déjà vu is directly linked to the function of these brain structures. We think that it is probably a certain small “error in the system” caused by higher excitability of hippocampuses. It is the consequence of changes in the most sensitive brain regions which probably occurred in the course of the development of the neural system.”
Experts say déjà vu, while fascinating, is not an uncommon experience. Between 60% and 80% of healthy individuals have reported occasional occurrences of déjà vu.
If you’re going to be a bug, you might as well be the most badass bug in existence. And a good candidate for such a title might go to the assassin bug of Malaysia, a predatory insect that wears the bodies of its slain victims all over its body as armor. That’s what I would do if I were a bug.