Subcellular vasopressin mRNA trafficking and local translation in dendrites

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Subcellular localization of mRNAs relies on cis-acting elements and trans-acting factors for transport along the cytoskeleton.
• Vasopressin mRNA is known to be delivered to both axons and dendrites in rat hypothalamic magnocellular neurons.

Purpose of the Study:

• To investigate the mechanisms of vasopressin mRNA localization to neuronal dendrites.
• To identify the cis-acting elements and trans-acting factors involved in vasopressin mRNA transport and local translation.

Main Methods:

• Microinjection of a eukaryotic expression vector encoding vasopressin mRNA into cultured neurons.
• Detailed analysis of RNA sequences to identify cis-acting elements (dendritic localizer sequence - DLS).
• Biochemical assays to investigate protein interactions with the DLS, specifically poly(A)-binding protein (PABP).
• Microinjection of a mutant vasopressin polyprotein construct to assess local synthesis in dendrites.

Main Results:

• Vasopressin mRNA, when microinjected, is sorted to dendrites in cultured neurons.
• A complex cis-acting element, the dendritic localizer sequence (DLS), was identified within the vasopressin mRNA.
• Poly(A)-binding protein (PABP) specifically interacts with the DLS, suggesting its role in RNA transport and regulation.
• Local synthesis of the vasopressin precursor in dendrites was confirmed using a non-diffusible mutant protein.

Conclusions:

• The dendritic localizer sequence (DLS) in vasopressin mRNA, in conjunction with poly(A)-binding protein (PABP), mediates dendritic mRNA transport.
• PABP is a likely component of a complex regulating vasopressin mRNA transport and local translation.
• Dendrites are sites of local protein synthesis for vasopressin precursors, as demonstrated by the expression of a localized mutant protein.