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. Author manuscript; available in PMC: 2020 Sep 14.
Published in final edited form as: Neurosci Lett. 2019 Jul 8;709:134373. doi: 10.1016/j.neulet.2019.134373

Figure 6. Novel roles for Gpsm2-Gαi and planar polarity in hair cells.

Figure 6.

A) At the IHC apical membrane, Gpsm2-Gαi is required for stereocilia elongation and graded heights across stereocilia rows. Gpsm2 and Gαi proteins (green, arrows) are localized at the tip and near the base of stereocilia in the first row, being planar polarized at the lateral bare zone. This dual distribution suggests that planar polarity might play a role in the restriction of Gpsm2-Gαi trafficking to first row stereocilia, establishing their tallest identity and regulating hair bundle staircase-like architecture. At the basolateral IHC membrane, both Gpsm2 and Gαi are required for the medial-lateral gradient of ribbon synapse (orange) size and synaptic activity. The IHC ribbon synapse releases neurotransmitters onto spiral ganglion neuron (SGN) afferent terminals (blue). B) In absence of Gpsm2-Gαi function, stereocilia fail to elongate at postnatal stages and the hair bundle retains an immature morphology with an excess number of rows, and the gradient of ribbon synapse size is abolished. It remains unclear how Gpsm2-Gαi proteins influence synapse size and activity.