Aquaporin 4 beyond a water channel; participation in motor, sensory, cognitive and psychological performances, a comprehensive review

•The role of AQP4 in the motor function is evidenced by participating in motor neuron survival after insult, and also locomotor functional recovery in neurological diseases through affecting muscular strength, motor speed and coordination, and finally motor learning.•AQP4 is essential for normal functioning of different sensory functions as special senses (vision, audition, olfaction) and somatosensory sensations (pain and thermal sensation).•AQP4 participates in various cognitive functions as the basic synaptic plasticity abilities, different memory functions, and aversive motivation for learning.•AQP4 can participate in psychological dysfunctions and diseases such as depression, anxiety, stress, addiction, and schizophrenia.•Due to the important role of AQP4 in different functions, its deficiency (up-regulation or down-regulation) can eventually lead to cell death and the following functional impairments which seem to be related to the type of function and the provoked disease model or neurological disease.•So, AQP4’s functional modulation can be a promising treatment target to improve different functional impairments separately or concurrently, specifically those related to the neurological disorders that must be further investigated in the future. Aquaporin 4 (AQP4) is a protein highly expressed in the central nervous system (CNS) and peripheral nervous system (PNS) as well as various other organs, whose different sites of action indicate its importance in various functions. AQP4 has a variety of essential roles beyond water homeostasis. In this article, we have for the first time summarized different roles of AQP4 in motor and sensory functions, besides cognitive and psychological performances, and most importantly, possible physiological mechanisms by which AQP4 can exert its effects. Furthermore, we demonstrated that AQP4 participates in pathology of different neurological disorders, various effects depending on the disease type. Since neurological diseases involve a spectrum of dysfunctions and due to the difficulty of obtaining a treatment that can simultaneously affect these deficits, it is therefore suggested that future studies consider the role of this protein in different functional impairments related to neurological disorders simultaneously or separately by targeting AQP4 expression and/or polarity modulation.