Research has linked the disease to a genetic defect that stops cells clearing out defective mitochondria, tiny metabolic generators that supply energy.
Dysfunctional mitochondria can be very harmful. Cells normally dispose of them through a process called mitophagy that breaks them down.
Scientists have now discovered a biological pathway that allows mutations in a gene called FBxo7 to interfere with mitophagy.
In people with Parkinson's, this causes a build-up of defective mitochondria that may kill brain cells.
A study published in the journal Nature Neuroscience indicates mitophagy might be the key to new treatments for the disease.
Dr Helene Plun-Favreau, one of the researchers from the University College London Institute of Neurology, said: "Treatment strategies that target mitophagy might be developed to benefit patients with Parkinson's disease in the future.
"What makes the study so robust is the confirmation of defective mitophagy in a number of different Parkinson's models."
Professor Hugh Perry, chair of the neurosciences and mental health board at the Medical Research Council which part-funded the study, said the work raised interesting questions about brain-cell death related to Parkinson's.
He added: "The more we understand about the basic molecular events which contribute to the onset and progression of Parkinson's disease, the better placed we will be to develop treatments."