A fluorescent biosensor for the visualization of agmatine

Agmatine is known to regulate various neurotransmitter systems, yet the underlying molecular mechanisms remain elusive. To visualize agmatine dynamics in cellular networks and thereby unravel its physiological functions, we developed a genetically encoded fluorescent agmatine biosensor (AGMsen) based on the periplasmic putrescine binding protein PotF. We first analyzed the agmatine binding properties of the PotF receptor module based on its crystal structure and introduced mutations into the binding pocket to favor agmatine binding over other biogenic amines. Validation of AGMsen functionality across different cell types, including primary neuronal cultures, demonstrates its ability of real-time agmatine visualization. Thus, the sensor can serve as a valuable tool to advance our understanding of agmatine distribution and dynamics, and shed light on their effect on neuronal functions in vivo .