Zipcode Binding Protein 1 Regulates the Development of Dendritic Arbors in Hippocampal Neurons

Abstract

The pattern of dendritic branching, together with the density of synapses and receptor composition, defines the electrical properties of a neuron. The development of the dendritic arbor and its additional stabilization are highly orchestrated at the molecular level and are guided by intrinsic mechanisms and extracellular information. Although protein translation is known to contribute to these processes, the role of its local component has not been fully explored. For local translation, mRNAs are transported to dendrites in their dormant form as ribonucleoparticles (RNPs). We hypothesized that disturbing spatial mRNA distribution via RNP targeting may result in severe underdevelopment of the dendritic arbor. Zipcode binding protein 1 (ZBP1) controls ␤-actin mRNA transport and translation in dendrites. We showed that proper cellular levels of ZBP1, its ability to engage in mRNA binding, and Src-dependent release of mRNA cargo from ZBP1 are vital for dendritic arbor development in cultured rat hippocampal neurons. Moreover, ␤-actin overexpression significantly alleviated the effects of ZBP1 knockdown. These results suggest that ZBP1-dependent dendritic mRNA transport contributes to proper dendritic branching.

Mammalian Target of Rapamycin Complex 1 (mTORC1) and 2 (mTORC2) Control the Dendritic Arbor Morphology of Hippocampal Neurons

“…Cell Cultures, Transfection, and Drug Treatment-HEK293 cell culture, their transfection, and Western blot analysis were performed as described recently (30). The animals used to obtain neurons for tissue cultures were sacrificed according to a protocol approved by the First Ethical Committee, Warsaw, Poland.…”

“…The animals used to obtain neurons for tissue cultures were sacrificed according to a protocol approved by the First Ethical Committee, Warsaw, Poland. Primary rat hippocampal and cortical cultures were prepared from embryonic day 18 (E18) rat brains according to Banker and Goslin (31) with modifications and transfected with Lipofectamine2000 (Invitrogen) as recently described (8,30). For insulin-induced growth, immediately after transfection, the cells were transferred to a regular culture medium that contained a reduced concentration of B27 (0.2% instead of 2%; Invitrogen).…”

“…The confocal settings were kept the same for all scans when the fluorescence intensities of immunostaining in neuronal cell somas were compared. Morphometric analysis and quantification were performed as recently described (8,30). For time-lapse imaging, neurons were imaged with an Olympus ScanR Station microscope with a 20ϫ objective with 1000 ϫ 1000 pixel resolution.…”

“…Thus, we repeated the transfection described above but focused specifically on the morphometric analysis of several parameters that describe dendritic arbor morphology (8,30). As shown in Fig.…”

BDNF-induced local protein synthesis and synaptic plasticity

“…BDNF signaling induces the phosphorylation of ZBP1 and local synthesis of b-actin in growth cones, contributing to growth cone turning (Sasaki et al, 2010). In a recent study, ZBP1 was shown to regulate dendritic branching (Perycz et al, 2011). Interestingly, knockdown of ZBP1 inhibited the growth of dendritic protrusions in response to BDNF stimulation (Eom et al, 2003), suggesting that under limiting amounts of ZBP1 and b-actin mRNA in dendrites, neurons are not able to induce robust actin growth following stimulation with BDNF.…”