Putting the brakes on an enzyme might rescue neurons that are dying due to a type of Parkinson’s disease that’s caused by a single genetic mutation, according to a new Stanford Medicine-led study conducted in mice.
The genetic mutation causes an enzyme called leucine-rich repeat kinase 2, or LRRK2, to be overactive. Too much LRRK2 enzyme activity changes the structure of brain cells in a way that disrupts crucial communication between neurons that make the neurotransmitter dopamine and cells in the striatum, a region deep in the brain that is part of the dopamine system and is involved in movement, motivation and decision making.
The genetic mutation causes an enzyme called leucine-rich repeat kinase 2, or LRRK2, to be overactive. Too much LRRK2 enzyme activity changes the structure of brain cells in a way that disrupts crucial communication between neurons that make the neurotransmitter dopamine and cells in the striatum, a region deep in the brain that is part of the dopamine system and is involved in movement, motivation and decision making.
Cellular antennae
About 25% of Parkinson's disease cases are caused by genetic mutations, and the single genetic mutation that makes the LRRK2 enzyme too active is one of the most common. An overactive LRRK2 enzyme causes cells to lose their primary cilia, a cellular appendage that acts like an antenna, sending and receiving chemical messages. A cell that has lost its primary cilia is like your mobile phone when the network is down -- no messages come through or are sent.
In a healthy brain, many messages are sent back and forth between dopamine neurons in a region of the brain called the substantia nigra and the striatum. These cellular "conversations" are possible because dopamine neuron axons, which are tubular extensions coming off the cell body, reach all the way to the striatum to communicate with neurons and glia, cells that support neuronal function.
An important communication that is disrupted by too much LRRK2 enzyme activity occurs when dopamine neurons are stressed and release a signal in the striatum called sonic hedgehog (named after the cartoon character). In a healthy brain, it causes certain neurons and astrocytes, a type of glial support cell, in the striatum to produce proteins called neuroprotective factors. As their name suggests, these proteins help shield other cells from dying. When there is too much LRRK2 enzyme activity, many of the striatal cells lose their primary cilia -- and their ability to receive the signal from dopamine neurons. This disruption in sonic hedgehog signaling means that needed neuroprotective factors are not produced.
"Many kinds of processes necessary for cells to survive are regulated through cilia sending and receiving signals. The cells in the striatum that secrete neuroprotective factors in response to hedgehog signals also need hedgehog to survive. We think that when cells have lost their cilia, they are also on the pathway to death because they need cilia to receive signals that keep them alive," Pfeffer explained.
"Findings from this study suggest that inhibiting the LRRK2 enzyme could stabilize the progression of symptoms if patients can be identified early enough," said Suzanne Pfeffer, PhD, the Emma Pfeiffer Merner Professor in Medical Sciences and a professor of biochemistry. Researchers can mitigate overactive LRRK2 using MLi-2 LRRK2 kinase inhibitor, a molecule that attaches to the enzyme and decreases its activity.
Pfeffer added that because the genetic mutation is not the only way to end up with overactive LRRK2 enzyme, the inhibitor treatment might help with other types of Parkinson's disease or even other neurodegenerative diseases.
PS: More details from https://med.stanford.edu/news/all-news/2025/07/parkinsons-drug.html
The genetic mutation causes an enzyme called leucine-rich repeat kinase 2, or LRRK2, to be overactive. Too much LRRK2 enzyme activity changes the structure of brain cells in a way that disrupts crucial communication between neurons that make the neurotransmitter dopamine and cells in the striatum, a region deep in the brain that is part of the dopamine system and is involved in movement, motivation and decision making.
The genetic mutation causes an enzyme called leucine-rich repeat kinase 2, or LRRK2, to be overactive. Too much LRRK2 enzyme activity changes the structure of brain cells in a way that disrupts crucial communication between neurons that make the neurotransmitter dopamine and cells in the striatum, a region deep in the brain that is part of the dopamine system and is involved in movement, motivation and decision making.
Cellular antennae
About 25% of Parkinson's disease cases are caused by genetic mutations, and the single genetic mutation that makes the LRRK2 enzyme too active is one of the most common. An overactive LRRK2 enzyme causes cells to lose their primary cilia, a cellular appendage that acts like an antenna, sending and receiving chemical messages. A cell that has lost its primary cilia is like your mobile phone when the network is down -- no messages come through or are sent.
In a healthy brain, many messages are sent back and forth between dopamine neurons in a region of the brain called the substantia nigra and the striatum. These cellular "conversations" are possible because dopamine neuron axons, which are tubular extensions coming off the cell body, reach all the way to the striatum to communicate with neurons and glia, cells that support neuronal function.
An important communication that is disrupted by too much LRRK2 enzyme activity occurs when dopamine neurons are stressed and release a signal in the striatum called sonic hedgehog (named after the cartoon character). In a healthy brain, it causes certain neurons and astrocytes, a type of glial support cell, in the striatum to produce proteins called neuroprotective factors. As their name suggests, these proteins help shield other cells from dying. When there is too much LRRK2 enzyme activity, many of the striatal cells lose their primary cilia -- and their ability to receive the signal from dopamine neurons. This disruption in sonic hedgehog signaling means that needed neuroprotective factors are not produced.
"Many kinds of processes necessary for cells to survive are regulated through cilia sending and receiving signals. The cells in the striatum that secrete neuroprotective factors in response to hedgehog signals also need hedgehog to survive. We think that when cells have lost their cilia, they are also on the pathway to death because they need cilia to receive signals that keep them alive," Pfeffer explained.
"Findings from this study suggest that inhibiting the LRRK2 enzyme could stabilize the progression of symptoms if patients can be identified early enough," said Suzanne Pfeffer, PhD, the Emma Pfeiffer Merner Professor in Medical Sciences and a professor of biochemistry. Researchers can mitigate overactive LRRK2 using MLi-2 LRRK2 kinase inhibitor, a molecule that attaches to the enzyme and decreases its activity.
Pfeffer added that because the genetic mutation is not the only way to end up with overactive LRRK2 enzyme, the inhibitor treatment might help with other types of Parkinson's disease or even other neurodegenerative diseases.
PS: More details from https://med.stanford.edu/news/all-news/2025/07/parkinsons-drug.html
