Date of Award

2016-01-01

Degree Name

Master of Science

Department

Biological Sciences

Advisor(s)

Sukla Roychowdhury

Abstract

Assembly and disassembly of microtubules is critical for axon and dendrite formation and neurite outgrowth. Previous studies have shown that βγ subunits of heterotrimeric G proteins promote microtubule (MT) assembly in vitro and in cultured PC12 cells. Recently, it was found that the interaction of Gβγ with MTs is important for nerve growth factor (NGF)-induced neuronal differentiation of PC12 cells and that the blocking of the interaction between Gβγ and tubulin/MT disrupted MTs, inhibited neurite outgrowth and induced axonal damage indicating the involvement of Gβγ in these processes. A different pathway involving the receptor tyrosine kinase (TrkA) and its downstream effector Phosphatidyl inositol-3-kinase (PI3K) has been shown to modulate neuronal differentiation. PI3K downstream effectors AKT and GSK-3β, have been shown to participate in the regulation of neurite outgrowth, and are particularly associated with microtubule remodeling. The current investigation is based on our hypothesis that Gβγ and PI3Kinase pathway co-ordinate to regulate neurite outgrowth by modulating MT assembly. Overexpression of Gβγ, and inhibitors of Gβγ (Gallein) and PI3K (LY294002) were used to identify the role of Gβγ/PI3K signaling in regulating neuronal differentiation and morphology. Neuronal differentiation of PC12 cells induced by NGF or Gβγ overexpression promoted the activation of PI3k/AKT/GSK-3β pathway supporting the idea that Gβγ and PI3K pathway works in concert. Both gallein and LY294002 inhibited the phosphorylation of AKT. However, stimulation of phosphorylation of GSK-3β was only partially inhibited by LY294002 while gallein was vii ineffective in reversing the effect of Gβγ overexpression. Both gallein and LY294002 disrupted neurite formation and altered cellular morphology. Our result suggests that Gβγ/PI3K pathway is involved in neuronal differentiation by regulating assembly and organization of microtubules. Because neurodegenerative and neuropsychiatric diseases are associated with alterations in neuronal cytoskeleton, these results will increase our understanding of the molecular basis of neurological diseases and strategies to develop novel drugs to treat them.

Language

en

Provenance

Received from ProQuest

File Size

67 pages

File Format

application/pdf

Rights Holder

Jose L. Varela

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Included in

Biology Commons

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