Human Doppel and prion protein share common membrane microdomains and internalization pathways

Area of Science:

• Neuroscience
• Molecular Biology
• Prion Biology

Background:

• Doppel is a homologue of the prion protein (PrPc) and shares structural similarities.
• Overexpression of Doppel in PrP knockout animals causes cerebellar ataxia, suggesting potential functional antagonism with PrPc.
• Recent observations indicate a direct interaction between Doppel and PrPc.

Purpose of the Study:

• To investigate the potential for interaction between human Doppel and PrPc in a neuronal cell model.
• To determine if Doppel and PrPc can co-exist and interact within the cellular environment of neuroblastoma cells.

Main Methods:

• Expression of human Doppel and PrPc, individually and together, in neuroblastoma cells.
• Biochemical and immunomicroscopic analyses.
• Study of fluorescent fusion constructs in intact cells.
• Investigation of protein behavior upon ganglioside cross-linking (cholera toxin) or antibody addition.
• Assessment of lipid raft integrity and protein localization within membrane microdomains (Triton X-100 solubility).

Main Results:

• Doppel and PrPc extensively co-patch at the plasma membrane when co-expressed.
• Both proteins are internalized together following cross-linking of gangliosides or antibody-mediated clustering of either protein.
• These co-trafficking events are dependent on the integrity of lipid rafts.
• Individually expressed proteins reside in Triton X-100-insoluble microdomains; co-expression leads to redistribution into less ordered lipid environments.

Conclusions:

• Doppel and PrPc interact within the plasma membrane of neuronal cells.
• Their co-localization and co-internalization suggest a functional relationship mediated by lipid rafts.
• The findings support the hypothesis of Doppel and PrPc interacting in a neuronal context.