Dopamine is a chemical messenger in thebrain. Learn about its role in mental illness, addiction and Parkinson’s disease, and medicines for imbalances. Parkinson's disease is a progressive movement disorder, affecting as many as 1 million people in the United States and 7 million to 10 million people worldwide, according to the Parkinson's Disease Foundation . The protein, called alpha-synuclein, is abundant in thebrain . Scientists still do not fully understand how α-synuclein moves between cells. A new study in Nature Communications points to two membrane proteins, mGluR4 and NPDC1, as important factors that help carry misfolded α-synuclein into healthy neurons after it is released by dying ones. Parkinson’s disease and Lewy Body Dementia are two serious brain disorders that affect millions of people around the world. These diseases slowly damage brain cells and can greatly affect daily life. Parkinson's disease (PD) is a progressive neurological disorder that primarily affects movement. It occurs when brain cells in the substantia nigra, an area responsible for producing dopamine, begin to deteriorate. People with Parkinson’s disease (PD) frequently experience gastrointestinal (GI) symptoms that can affect daily function, medication response, nutrition, swallowing safety, and quality of life. The gut is also increasingly recognized as a trigger for brain diseases like PD.