Gβγ-Microtubule Interaction and Neurodegeneration

Aberrant organization of microtubules (MTs) is known to be a feature of neurodegeneration, which occurs in many neurological disorder including Alzheimer’s disease, Parkinson’s disease, neuropsychiatric illness such as schizophrenia, and drug addiction. Previously, Gβγ, an important component of G protein-coupled signaling pathways, has been shown to regulate neurite outgrowth by interacting with MTs. The aim of the present study is to understand the Gβγ regulation of MT assembly and its relation to neurodegeneration, using GRK-ct peptide (consists of the carboxy terminus of G protein-coupled-receptor kinase) which is known to inhibit Gβγ-dependent signaling by binding to and sequestering Gβγ. PC12 cells were used to conduct the study because they respond to nerve growth factor (NGF) with growth arrest and exhibit a typical phenotype of neuronal cells sending out neurites. PC12 cells were treated with NGF over the course of three days followed by treatment with GRK-ct peptide for 1h, and the result was evaluated by subcellular fractionation, and confocal microscopy. Confocal microscopy revealed that the GRK-ct peptide has a very dramatic effect on morphology and survival of NGF-differentiated PC12 cells, causing cellular aggregation, neurite and MT disruption, and severe degeneration. Interestingly, the levels of MAP2, a cytoskeletal protein that stabilizes MTs, dramatically decreased in the presence of GRK-ct peptide. The results indicate that the inhibition of Gβγ-dependent signaling induce cytoskeletal alterations and neurodegeneration. Future investigation will address whether Gβγ signaling could be targeted for developing novel drugs against drug addiction and other neurodegenerative disorders