Final answer:
Huntington's Disease (HD) is not solely a result of the loss of normal function of the huntingtin protein but also involves the dysregulation of NMDA receptors and the toxic accumulation of the mutated protein. This pathological mechanism is consistent with the concept of 'proteopathy', which is a common theme in neurodegenerative diseases such as Alzheimer's and Parkinson's.
Step-by-step explanation:
The proof that more than just the loss of normal function of huntingtin protein leads to Huntington's Disease (HD) lies in the understanding of the disease mechanism. The mutation resulting in HD produces a huntingtin protein with a longer sequence of glutamine residues, and while it used to be thought that dysfunction of this protein caused the disease's symptoms, this is only part of the story. Research has shown that the mutated huntingtin protein causes dysregulation in the expression of NMDA receptors, notably the extrasynaptic ones, which increase intracellular calcium concentrations in ways that lead to neuron cell death. This mechanism indicates that HD involves not only the loss of a protein's normal function but also the acquisition of new, harmful functions by the altered protein that contribute to the neural damage observed in the disease.
The underlying mechanism of many neurodegenerative diseases, including HD, is the concept of 'proteopathy', where misfolded or abnormally accumulated proteins lead to cell toxicity. This is similar to other proteopathic diseases like Alzheimer's and Parkinson's, where the accumulation of toxic proteins is central to the disease process. The mutant huntingtin protein's propensity to accumulate and disrupt normal cellular functions offers a potential target for therapeutic intervention, focusing on preventing the toxic accumulation rather than just supplementing the lost function.