PT  - JOURNAL ARTICLE
AU  - Jisoo S. Han
AU  - Keiko Hino
AU  - Raenier V. Reyes
AU  - Cesar P. Canales
AU  - Adam M. Miltner
AU  - Yasmin Haddadi
AU  - Junqing Sun
AU  - Chao-Yin Chen
AU  - Anna La Torre
AU  - Sergi Simó
TI  - CRL5-dependent regulation of Arl4c and Arf6 controls hippocampal morphogenesis
AID  - 10.1101/2020.01.10.902221
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.01.10.902221
4099  - http://biorxiv.org/content/early/2020/01/11/2020.01.10.902221.short
4100  - http://biorxiv.org/content/early/2020/01/11/2020.01.10.902221.full
AB  - The small GTPase Arl4c participates in the regulation of cell migration, cytoskeletal rearrangements, and vesicular trafficking in epithelial cells. The Arl4c signaling cascade starts by the recruitment of the Arf-GEF cytohesins to the plasma membrane, which in turn engage the small GTPase Arf6. In the nervous system, Arf6 regulates dendrite outgrowth in vitro and neuronal migration in the developing cortex. However, the role of Arl4c-cytohesin-Arf6 signaling during brain development and particularly during hippocampal development remain elusive. Here, we report that the E3 ubiquitin ligase Cullin 5/Rbx2 (CRL5) controls the stability of Arl4c and its signaling effectors to regulate hippocampal morphogenesis. Rbx2 knock out causes hippocampal pyramidal neuron mislocalization and formation of multiple apical dendrites. The same phenotypes were observed when Cullin 5 was knocked down in pyramidal neurons by in utero electroporation. We used quantitative mass spectrometry to show that Arl4c, Cytohesin-1/3, and Arf6 accumulate in the telencephalon when Rbx2 is absent. Arl4c expression is post-transcriptionally regulated, with a peak in expression at early postnatal stages, and is localized at the plasma membrane and on intracellular vesicles in hippocampal pyramidal neurons. Furthermore, we show that depletion of Arl4c rescues the phenotypes caused by Cullin 5 knock down in the hippocampus, whereas depletion of Arf6 exacerbates over-migration. Finally, we show that Arl4c and Arf6 are necessary for the dendritic outgrowth of pyramidal neurons to the most superficial strata of the hippocampus. Overall, we identified CRL5 as a key regulator of hippocampal development and uncovered Arl4c and Arf6 as novel CRL5-regulated signaling effectors that control pyramidal neuron migration and dendritogenesis.