PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Surprising solution to fly eye mystery

Research provides insight into why flies have the fastest vision in the animal kingdom

2012-10-12
(Press-News.org) Fly eyes have the fastest visual responses in the animal kingdom, but how they achieve this has long been an enigma. A new study shows that their rapid vision may be a result of their photoreceptors - specialised cells found in the retina - physically contracting in response to light. The mechanical force then generates electrical responses that are sent to the brain much faster than, for example, in our own eyes, where responses are generated using traditional chemical messengers. The study was published today, 12 October, in the journal Science.

It had been thought that the ion channels responsible for generating the photoreceptors' electrical response were activated by chemical messengers as is usually the case in cell signalling pathways. However, these results suggest that the light-sensitive ion channels responsible for the photoreceptor's electrical response may be physically activated by the contractions – a surprising solution to the mystery of light perception in the fly's eye and a new concept in cellular signalling.

Professor Roger Hardie, lead author of the study from the University of Cambridge's Department of Physiology, Development and Neuroscience, said: "The ion channel in question is the so-called 'transient receptor potential' (TRP) channel, which we originally identified as the light-sensitive channel in the fly in the 1990's. It is now recognised as the founding member of one of the largest ion channel families in the genome, with closely related channels playing vital roles throughout our own bodies. As such, TRP channels are increasingly regarded as potential therapeutic targets for numerous pathological conditions, including pain, hypertension, cardiac and pulmonary disease, cancer, rheumatoid arthritis, and ce rebral ischaemia. We are therefore hopeful that these new results may have significance well beyond the humble eye of the fly."

A fly's vision is so fast that it is capable of tracking movements up to five times faster than our own eyes. This performance is achieved using microvillar photoreceptor cells, in which the photo-receptive membrane is made up of tiny tubular membranous protrusions known as microvilli. In each photoreceptor cell, tens of thousands of these are packed together to form a long rod-like structure, which acts as a light-guide to absorb the incident light. Each microvillus also houses the biochemical machinery, which converts the energy of the absorbed light into the electrical responses that are sent to the brain – a process known as phototransduction.

As in all photoreceptors, phototransduction starts with absorption of light by a visual pigment molecule (rhodopsin). In microvillar photoreceptors this leads to activation of a specific enzyme known as phospholipase C (PLC). PLC is a ubiquitous and very well-studied enzyme, which cleaves a large piece from a specific lipid component of the cell membrane ("PIP2"), leaving a smaller membrane lipid (DAG) in its place.

Somehow this enzymatic reaction leads to the opening of "ion channels" in the microvillus membrane; once opened, these allow positively charged ions such as Ca2+ and Na+ to flow into the cell thus generating the electrical response. This basic sequence of events has been established for over 20 years; but exactly how PLC's enzymatic activity causes the opening of the channels has long remained a mystery and one of the major outstanding questions in sensory biology.

Professor Hardie added: "The conventional wisdom would be that one of the products of this enzyme's activity is a chemical 'second messenger' that binds to and activates the channel. However, years of research had previously failed to find compelling evidence for such a straightforward mechanism."

The new study, which was funded by the BBSRC and the Medical Research Council, using the fruitfly, Drosophila, now suggests a remarkable and unexpected resolution to this mystery. The key finding was that the photoreceptors physically contract in response to light flashes. The contractions were so small and fast that an "atomic force microscope" was needed to measure them. This revealed that the contractions were even faster than the cell's electrical response and appeared to be caused directly by PLC activity.

The researchers believe that the splitting of the membrane lipid PIP2 by the enzyme PLC reduces the membrane area, thereby increasing tension in the membrane and causing each tiny microvillus to contract in response to light. The synchronised contraction of thousands of microvilli together then accounts for the contractions measured from the whole cell.

Dr Kristian Franze, co-author of the paper from the University of Cambridge, said: "We propose that within each microvillus the increase in membrane tension acts directly on the light-sensitive channels. In other words, rather than using a traditional chemical 2nd messenger, the channels were being activated mechanically."

This concept was supported by experiments in which the native light-sensitive channels were eliminated by mutation and replaced with mechano-sensitive channels, which are known to open in response to membrane tension. Remarkably, these photoreceptors still generated electrical signals in response to light, but were now mediated by activation of the ectopic mechano-sensitive channels. To test whether the native light-sensitive channels could be affected by mechanical forces in the membrane, the microvillar membrane was stretched or compressed by changing the osmotic pressure. This simple experimental manipulation rapidly enhanced or suppressed channel openings in response to light as predicted.

These results suggest that PLC mediates its effects in the photoreceptors by changing the mechanical state of the membrane. The researchers suggest that it is the increase in the membrane tension (along with a pH change also resulting from PLC activity) that triggers the opening of the light-sensitive channels. Mechano-sensitive ion channels are actually well known, but normally involved in transducing mechanical stimuli – such as sound in the ears or pressure on the skin. One of their characteristics is that they can be activated extremely rapidly – perhaps an explanation for why fly photoreceptors have evolved this solution to phototransduction.

Professor Hardie said: "That a mechanical signal could be an intermediate signal -or 'second messenger'- in an otherwise purely biochemical cascade is a novel concept that extends our understanding of cellular signalling mechanisms to a new level." ###

For additional information please contact:

Genevieve Maul, Office of Communications, University of Cambridge
Tel: direct, +44 (0) 1223 765542, +44 (0) 1223 332300
Mob: +44 (0) 7774 017464
Email: Genevieve.maul@admin.cam.ac.uk

Notes to editors:

1. The paper 'Photomechanical responses in Drosophila photoreceptors' is scheduled to be published in Science on 12 October 2012.

2. Videos and images available.

3. About BBSRC - BBSRC is the UK funding agency for research in the life sciences and the largest single public funder of agriculture and food-related research.

Sponsored by Government, in 2010/11 BBSRC is investing around £470 million in a wide range of research that makes a significant contribution to the quality of life in the UK and beyond and supports a number of important industrial stakeholders, including the agriculture, food, chemical, healthcare and pharmaceutical sectors.

BBSRC provides institute strategic research grants to the following:

The Babraham Institute, Institute for Animal Health, Institute for Biological, Environmental and Rural Studies (Aberystwyth University), Institute of Food Research, John Innes Centre, The Genome Analysis Centre, The Roslin Institute (University of Edinburgh) and Rothamsted Research.

The Institutes conduct long-term, mission-oriented research using specialist facilities. They have strong interactions with industry, Government departments and other end-users of their research. For more information see: http://www.bbsrc.ac.uk

4. The Medical Research Council (MRC) is a publicly-funded organisation. Its business is medical research aimed at improving human health. The research it supports and the scientists it trains meet the needs of the health services, the pharmaceutical and other health-related industries and the academic world. MRC has funded work which has led to some of the most significant discoveries and achievements in medicine in the UK.

For more information, see: http://www.mrc.ac.uk/index.htm



ELSE PRESS RELEASES FROM THIS DATE:

Weizmann Institute Scientists observe quantum effects in cold chemistry

Weizmann Institute Scientists observe quantum effects in cold chemistry
2012-10-12
At very low temperatures, close to absolute zero, chemical reactions may proceed at a much higher rate than classical chemistry says they should – because in this extreme chill, quantum effects enter the picture. A Weizmann Institute team has now confirmed this experimentally; their results would not only provide insight into processes in the intriguing quantum world in which particles act as waves, it might explain how chemical reactions occur in the vast frigid regions of interstellar space. Long-standing predictions are that quantum effects should allow the formation ...

Developmental biologist proposes new theory of early animal evolution

2012-10-12
VALHALLA, October 11, 2012—A New York Medical College developmental biologist whose life's work has supported the theory of evolution has developed a concept that dramatically alters one of its basic assumptions—that survival is based on a change's functional advantage if it is to persist. Stuart A. Newman, Ph.D., professor of cell biology and anatomy, offers an alternative model in proposing that the origination of the structural motifs of animal form were actually predictable and relatively sudden, with abrupt morphological transformations favored during the early period ...

Alzheimer's sufferers may function better with less visual clutter

Alzheimers sufferers may function better with less visual clutter
2012-10-12
TORONTO, ON – Psychologists at the University of Toronto and the Georgia Institute of Technology – commonly known as Georgia Tech – have shown that an individual's inability to recognize once-familiar faces and objects may have as much to do with difficulty perceiving their distinct features as it does with the capacity to recall from memory. A study published in the October issue of Hippocampus suggests that memory impairments for people diagnosed with early stage Alzheimer's disease may in part be due to problems with determining the differences between similar objects. ...

Exercise helps ease premature cardiovascular aging caused by type 2 diabetes

2012-10-12
WESTMINSTER, CO (October 10, 2012)—One of life's certainties is that everyone ages. However, it's also certain that not everyone ages at the same rate. According to recent research being presented this week, the cardiovascular system of people with type 2 diabetes shows signs of aging significantly earlier than those without the disease. However, exercise can help to slow down this premature aging, bringing the aging of type 2 diabetes patients' cardiovascular systems closer to that of people without the disease, says researcher Amy Huebschmann of the University of Colorado ...

Exercise could fortify immune system against future cancers

2012-10-12
WESTMINSTER, CO (October 10, 2012)—Researchers may soon be able to add yet another item to the list of exercise's well-documented health benefits: A preliminary study suggests that when cancer survivors exercise for several weeks after they finish chemotherapy, their immune systems remodel themselves to become more effective, potentially fending off future incidences of cancer. The finding may help explain why exercise can significantly reduce the chances of secondary cancers in survivors or reduce the chances of cancer altogether in people who have never had the disease. Laura ...

Parental bonding makes for happy, stable child

Parental bonding makes for happy, stable child
2012-10-12
Parents: Want to help ensure your children turn out to be happy and socially well adjusted? Bond with them when they are infants. That's the message from a study by the University of Iowa, which found that infants who have a close, intimate relationship with a parent are less likely to be troubled, aggressive or experience other emotional and behavioral problems when they reach school age. Surprisingly, the researchers found that a young child needs to feel particularly secure with only one parent to reap the benefits of stable emotions and behavior, and that being attached ...

Minutes of hard exercise can lead to all-day calorie burn

2012-10-12
WESTMINSTER, CO (October 10, 2012)—Time spent in the drudgery of strenuous exercise is a well-documented turn-off for many people who want to get in better shape. In a new study, researchers show that exercisers can burn as many as 200 extra calories in as little as 2.5 minutes of concentrated effort a day—as long as they intersperse longer periods of easy recovery in a practice known as sprint interval training. The finding could make exercise more manageable for would-be fitness buffs by cramming truly intense efforts into as little as 25 minutes. Kyle Sevits, Garrett ...

Focus on space debris: Envisat

2012-10-12
Space debris came into focus last week at the International Astronautical Congress in Naples, Italy. Envisat, ESA's largest Earth observation satellite, ended its mission last spring and was a subject of major interest in the Space Debris and Legal session. Envisat was planned and designed in 1987, a time when space debris was not considered to be a serious problem and before the existence of mitigation guidelines, established by the UN in 2007 and adopted the next year by ESA for all of its projects. Only later, during the post-launch operational phase, did Envisat's ...

Discovery reveals important clues to cancer metastasis

2012-10-12
BOSTON – In recent years investigators have discovered that breast tumors are influenced by more than just the cancer cells within them. A variety of noncancerous cells, which in many cases constitute the majority of the tumor mass, form what is known as the "tumor microenvironment." This sea of noncancerous cells and the products they deposit appear to play key roles in tumor pathogenesis. Among the key accomplices in the tumor microenvironment are mesenchymal stem cells (MSCs), a group of adult progenitor cells which have been shown to help breast cancers maneuver and ...

Nerve and muscle activity vary across menstrual cycle

2012-10-12
WESTMINSTER, CO (October 10, 2012)—Numerous studies have shown that female athletes are more likely to get knee injuries, especially anterior cruciate ligament (ACL) tears and chronic pain, than their male counterparts. While previous research has focused on biomechanical differences as the main source of these problems, a new study suggests another distinction that could play a role: changes across the menstrual cycle in nerves that control muscle activity. The finding may eventually lead to new ways to prevent knee problems in female athletes. Matthew Tenan, Yi-Ling ...

LAST 30 PRESS RELEASES:

Program takes aim at drinking, unsafe sex, and sexual assault on college campuses

Inability to pay for healthcare reaches record high in U.S.

Science ‘storytelling’ urgently needed amid climate and biodiversity crisis

KAIST Develops Retinal Therapy to Restore Lost Vision​

Adipocyte-hepatocyte signaling mechanism uncovered in endoplasmic reticulum stress response

Mammals were adapting from life in the trees to living on the ground before dinosaur-killing asteroid

Low LDL cholesterol levels linked to reduced risk of dementia

Thickening of the eye’s retina associated with greater risk and severity of postoperative delirium in older patients

Almost one in ten people surveyed report having been harmed by the NHS in the last three years

Enhancing light control with complex frequency excitations

New research finds novel drug target for acute myeloid leukemia, bringing hope for cancer patients

New insight into factors associated with a common disease among dogs and humans

Illuminating single atoms for sustainable propylene production

New study finds Rocky Mountain snow contamination

Study examines lactation in critically ill patients

UVA Engineering Dean Jennifer West earns AIMBE’s 2025 Pierre Galletti Award

Doubling down on metasurfaces

New Cedars-Sinai study shows how specialized diet can improve gut disorders

Making moves and hitting the breaks: Owl journeys surprise researchers in western Montana

PKU Scientists simulate the origin and evolution of the North Atlantic Oscillation

ICRAFT breakthrough: Unlocking A20’s dual role in cancer immunotherapy

How VR technology is changing the game for Alzheimer’s disease

A borrowed bacterial gene allowed some marine diatoms to live on a seaweed diet

Balance between two competing nerve proteins deters symptoms of autism in mice

Use of antifungals in agriculture may increase resistance in an infectious yeast

Awareness grows of cancer risk from alcohol consumption, survey finds

The experts that can outsmart optical illusions

Pregnancy may reduce long COVID risk

Scientists uncover novel immune mechanism in wheat tandem kinase

Three University of Virginia Engineering faculty elected as AAAS Fellows

[Press-News.org] Surprising solution to fly eye mystery
Research provides insight into why flies have the fastest vision in the animal kingdom