Table 1.

AQP4 isoforms affect the abundance and size of OAPs directly and indirectly.

AQP4 Isoform	Species/mRNA	Incorporation into OAPs	Reference
AQP4a (M1)	Human, rat, mouse/basic mRNA; posttranscriptional regulation defines the amount of protein in the plasma membrane	Yes (through interaction with AQP4c (M23))	[17,25,27,28,29,30,31,32]
AQP4a (M1) ex	Human, rat/extended mRNA through translational readthrough	Yes	[19]
AQP4c (M23)	Human, rat/basic mRNA; posttranscriptional regulation defines the amount of protein in the plasma membrane	Yes (it is the core OAP constituent)	[17,25,27,28,29,30,31,32]
AQP4c (M23) ex	Human, rat/extended mRNA through translational readthrough	Yes (modulates the size of OAPs by limiting the number of added tetramers)	[19]
AQP4e (Mz)	Rat/basic mRNA	Yes (through interaction with AQP4c (M23))	[8,23,29]
AQP4b	Rat/mRNA isoform lacking exon 2 after alternative splicing from AQP4a	No (indirect modulation of the abundance of OAPs)	[13,23]
AQP4d	Rat/mRNA isoform lacking exon 2 after alternative splicing from AQP4c	No (indirect modulation of the abundance of OAPs)	[13,23]
AQP4f	Rat/mRNA isoform lacking exon 2 after alternative splicing from AQP4c	Not tested	[23]
AQP4-Δ4	Human/mRNA isoform lacking exon 4 after alternative splicing from AQP4a	No (it may modulate the abundance and size of OAPs by dominant-negative effect exerted in endoplasmic reticulum through protein–protein interactions with the plasma membrane AQP4 isoforms)	[22]