Unearthing a pathway to brain damage

February 25, 2011, RIKEN
Figure 1: Cross-sections of the brain’s cerebellum showing normal neurons (left) and ones lacking IP3R1 (right), which results in abnormal cell death and brain damage under ER stress conditions. Credit: 2011 Elsevier Inc.

Neuroscientists have long suspected that abnormal calcium signaling and accumulation of misfolded proteins cause an intracellular membrane-bound organelle called the endoplasmic reticulum (ER) to trigger the abnormal death of cells implicated in many neurodegenerative diseases. However, the underlying mechanisms have proved elusive.

The ER is crucial for synthesizing proteins and maintaining their quality, and also acts as a reservoir of calcium ions essential for numerous cellular events. However, it is sensitive to alterations of surrounding environments, causing a process called ER stress.

Katsuhiko Mikoshiba and Takayasu Higo at the RIKEN Brain Science Institute, Wako, and their colleagues now report that a called IP3 receptor type1 (IP3R1), which mediates the release of from ER, is destroyed by ER stress and that this induces neuronal cell death and brain damage1 (Fig. 1).

Using a calcium imaging technique, the researchers revealed that IP3R1 released less calcium in cultured neurons treated with an ER stress inducer than in controls. To investigate the significance of this dysfunction, they bred mice lacking the gene for IP3R1, which caused under ER stress conditions.

In an exploration into how ER stress impairs IP3R1 and induces neuronal cell death. Mikoshiba and colleagues identified GRP78, a molecular ‘chaperone’ that normally regulates the cellular response to misfolded proteins, as an interacting partner of IP3R1. RNA interference experiments revealed that GRP78 positively regulates the assembly of IP3R1, which consists of four subunits. They also found that this interaction was inhibited under ER stress conditions.

In a further set of experiments, the researchers then examined the involvement of the interaction in neurodegenerative diseases using a mouse model of Huntington’s disease (HD). They found that both the interaction and IP3R1 channel activity were significantly impaired in parts of the brain most affected in HD.

The findings demonstrate a novel mechanism by which ER stress impairs the regulation of IP3R1 by GRP78. Mikoshiba and Higo propose that IP3R1 functions to protect the brain against stress and that the link between ER stress, IP3/calcium signaling, and is associated with neurodegenerative disease.

“It has been suggested that neurodegenerative conditions including Huntington’s disease are associated with deranged calcium signaling and ER stress,” says Mikoshiba. “We hypothesize that IP3R1 functions to protect the brain from , so development of a method to restore or enhance IP3R1 could prevent disease progression or alleviate the symptoms. Our findings might be applied to other such as Alzheimer's disease.”

More information: Higo, T., et al. Mechanism of ER stress-induced brain damage by IP3 receptor. Neuron 68, 865–878 (2010). www.cell.com/neuron/abstract/S0896-6273(10)00917-7

Related Stories

Recommended for you

Newborn babies who suffered stroke regain language function in opposite side of brain

February 17, 2018
It's not rare that a baby experiences a stroke around the time it is born. Birth is hard on the brain, as is the change in blood circulation from the mother to the neonate. At least 1 in 4,000 babies are affected shortly ...

Lab-grown human cerebellar cells yield clues to autism

February 16, 2018
Increasing evidence has linked autism spectrum disorder (ASD) with dysfunction of the brain's cerebellum, but the details have been unclear. In a new study, researchers at Boston Children's Hospital used stem cell technology ...

Fragile X syndrome neurons can be restored, study shows

February 16, 2018
Fragile X syndrome is the most frequent cause of intellectual disability in males, affecting one out of every 3,600 boys born. The syndrome can also cause autistic traits, such as social and communication deficits, as well ...

Brain-machine interface study suggests how brains prepare for action

February 16, 2018
Somewhere right now in Pyeongchang, South Korea, an Olympic skier is thinking through the twists and spins she'll make in the aerial competition, a speed skater is visualizing how he'll sneak past a competitor on the inside ...

Humans blink strategically in response to environmental demands

February 16, 2018
If a brief event in our surroundings is about to happen, it is probably better not to blink during that moment. A team of researchers at the Centre for Cognitive Science from Technische Universität Darmstadt published a ...

Model for producing brain's 'helper cells' could lead to treatments for Alzheimer's

February 16, 2018
A Swedish research team has published a new protocol with the potential for industrial-scale production of the brain helper cells known as astrocytes. Their work could help medical science develop treatments for such diseases ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.