Unearthing a pathway to brain damage

Feb 25, 2011
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.”

Explore further: New mapping approach lets scientists zoom in and out as the brain processes sound

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

add to favorites email to friend print save as pdf

Related Stories

New mechanism links cellular stress and brain damage

Dec 08, 2010

A new study uncovers a mechanism linking a specific type of cellular stress with brain damage similar to that associated with neurodegenerative disease. The research, published by Cell Press in the December 9 issue of the ...

Cellular stress causes fatty liver disease in mice

Dec 08, 2008

A University of Iowa researcher and colleagues at the University of Michigan have discovered a direct link between disruption of a critical cellular housekeeping process and fatty liver disease, a condition that causes fat ...

Recommended for you

Steering the filaments of the developing brain

6 minutes ago

During brain development, nerve fibers grow and extend to form brain circuits. This growth is guided by molecular cues (Fig. 1), but exactly how these cues guide axon extension has been unclear. Takuro Tojima ...

Do we really only use 10% of our brain?

56 minutes ago

As the new film Lucy, starring Scarlett Johansson and Morgan Freeman is set to be released in the cinemas this week, I feel I should attempt to dispel the unfounded premise of the film – that we only use 10% of our brains ...

Birthday matters for wiring-up the brain's vision centers

21 hours ago

Researchers at the University of California, San Diego School of Medicine have evidence suggesting that neurons in the developing brains of mice are guided by a simple but elegant birth order rule that allows them to find ...

User comments : 0