P2Y1 Purinergic Receptor Modulate Axon Initial Segment Initial Development

Abstract

Morphological and functional polarization of neurons depends on the generation and maintenance of the axon initial segment (AIS). This axonal domain maintains axonal properties but is also the place where the action potential (AP) is generated. All these functions require the AIS, a complex structure that is not fully understood. An integrated structure of voltage-gated ion channels, specific cytoskeleton architecture, as well as, scaffold proteins contributes to these functions. Among them, ankyrinG plays a crucial role to maintain ion channels and membrane proteins. However, it is still elusive how the AIS performs its complex structural and functional regulation. Recent studies reveal that AIS is dynamically regulated in molecular composition, length and location in response to neuronal activity. Some mechanisms acting on AIS plasticity have been uncovered recently, including Ca 2+ , calpain or calmodulin-mediated modulation, as well as post-translational modifications of cytoskeleton proteins and actin-associated proteins. Neurons are able to respond to different kind of physiological and pathological stimuli from development to maturity by adapting their AIS composition, position and length. This raises the question of which are the neuronal receptors that contribute to the modulation of AIS plasticity. Previous studies have shown that purinergic receptor P2X7 activation is detrimental to AIS maintenance. During initial axonal elongation, P2X7 is coordinated with P2Y1, another purinergic receptor that is essential for proper axon elongation. In this study, we focus on the role of P2Y1 receptor on AIS development and maintenance. Our results show that P2Y1 receptor activity and expression are necessary during AIS initial development, while has no role once AIS maturity is achieved. P2Y1 inhibition or suppression results in a decrease in ankyrinG, βIV-spectrin and voltage-gated sodium channels accumulation that can be rescued by actin stabilization or the modulation of actin-binding proteins at the AIS. Moreover, P2X7 or calpain inhibition also rescues ankyrinG decrease. Hence, a dynamic balance of P2Y1 and P2X7 receptors expression and function during AIS assembly and maturation may represent a fine regulatory mechanism in response to physiological or pathological extracellular purines concentration.

Influence of spatially segregated IP 3 -producing pathways on spike generation and transmitter release in Purkinje cell axons

“…P2Y1Rs are well known to be associated to PLC activation (48); however, the exact nature of the linking G protein and of the PLC remains unclear, particularly in the nervous system. Our finding of P2Y1Rs in the AIS is consistent with earlier findings that in hippocampal cultures, P2Y1Rs regulate ankyrin G expression in the AIS (57). On the other hand, our finding of P2Y1Rs in PC terminals is consistent with earlier reports suggesting that P2Y1R activation elicits an enhancement of GABA release in hippocampal and cerebellar GABAergic axons (46,47).…”

The type 2 diabetes factor methylglyoxal mediates axon initial segment shortening and neuronal network activity changes

“…Images of immunostained coverslips were obtained using a fluorescence microscope (Axio Observer Z1 with Apotome 2 fitted with AxioCam Mrm CCD camera; Carl Zeiss) and measurement of axon initial segment length was performed using the curve spline measurement tool in ZEN2.0 (Carl Zeiss) or a Matlab script adapted from previous studies (Grubb and Burrone, 2010;Yau et al, 2014). Our comparison of AIS length measured by eye versus by custom Matlab script yielded similar results, which is consistent with a strong correlation (Spearman r > 0.8) of AIS length measured by eye with AIS measurement using custom-written Matlab scripts as reported previously (Grubb and Burrone, 2010;Evans et al, 2015;Guo et al, 2017;Fruscione et al, 2018;Zhang et al, 2019). Measurement of AIS location (distance from the edge of the soma to the start of the AIS) was performed as described previously (Guo et al, 2017).…”

The Type 2 Diabetes Factor Methylglyoxal Mediates Axon Initial Segment Shortening and Alters Neuronal Function at the Cellular and Network Levels

“…Images of immunostained coverslips were obtained using a fluorescence microscope (Axio Observer Z1 with Apotome 2 fitted with AxioCam Mrm CCD camera, Carl Zeiss Microscopy LLC, White Plains, 10 NY) and measurement of axon initial segment length was performed using the curve spline measurement tool in ZEN2.0 (Carl Zeiss) or a Matlab script adapted from previous studies (Grubb and Burrone, 2010;Yau et al, 2014). Our comparison of AIS length measured by eye versus by custom Matlab script yielded similar results, which is consistent with a strong correlation (Spearman r > 0.8) of AIS length measured by eye with AIS measurement using custom-written Matlab scripts as reported previously (Grubb and Burrone, 2010;Evans et al, 2015;Guo et al, 2017;Fruscione et al, 2018;Zhang et al, 2019). Measurement of AIS start location (distance from the edge of the soma to the start of the AIS) was performed as described previously (Guo et al, 2017).…”