Date of Degree

5-2019

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor

Mitchell Goldfarb

Committee Members

Jayne Raper

Paul Feinstein

Stephen Redenti

Geri Kreitzer

Subject Categories

Cell Biology | Developmental Biology | Genetics | Molecular and Cellular Neuroscience | Molecular Genetics

Keywords

ZBP1, PAT1, BDNF, β-actin mRNA, transport, RNA-binding protein, Synaptogenesis

Abstract

Cytoskeleton based active transport with motor proteins is essential for mRNA localization and local protein translation in animal cells, yet how mRNA granules interact with motor proteins remains poorly understood. Using an unbiased screen for interaction between mRNA binding proteins (RBP) and motor proteins, we identified protein interacting with APP tail 1 (PAT1) as a potential direct adapter between the β-actin mRNA Zipcode-binding protein 1 (ZBP1) and Kinesin-1 motor complex.

Mouse PAT1 is similar to the Kinesin Light Chain (KLC) in amino acid sequence and binds directly to KLC. High-resolution images from structured illumination microscopy (SIM) indicates that synaptic stimulation with Brain-derived neurotrophic factor (BDNF) enhances dendritic ZBP1 and PAT1 colocalization within ~100 nm granules, which also contain Kinesin-1.

PAT1 is essential for BDNF-stimulated dynamic actin reorganization in dendritic growth cones and filopodial protrusions during synaptogenesis. Both ZBP1 and PAT1 are co-visualized along with β-actin mRNA in actively transported granules in living dendrites with the help of genetically encoded fluorescent mRNA. Acute disruption of the PAT1-ZBP1 interaction diminishes the localization of β-actin mRNA but not the dendritic localization of Calcium/Calmodulin-dependent protein kinase II α (CaMKIIα) mRNA. The disruption also results in aberrant BDNF-induced dendritic morphologic plasticity and excitatory synapse formation. These data suggest a critical role for PAT1 in neurotrophin-induced β-actin mRNA transport during postnatal development that regulates dendrite growth and synapse function. It also reveals a new molecular mechanism for mRNA localization in vertebrates.

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