TY  - JOUR
A1  - Bülow, Julia von
A1  - Müller-Lucks, Annika
A1  - Kai, Lei
A1  - Bernhard, Frank
A1  - Beitz, Eric
T1  - Functional characterization of a novel aquaporin from Dictyostelium discoideum amoebae implies a unique gating mechanism
T2  - Journal of biological chemistry
N2  - The social amoeba Dictyostelium discoideum is a widely used model organism for studying basic functions of protozoan and metazoan cells, such as osmoregulation and cell motility. There is evidence from other species that cellular water channels, aquaporins (AQP), are central to both processes. Yet, data on D. discoideum AQPs is almost absent. Despite cloning of two putative D. discoideum AQPs, WacA, and AqpA, water permeability has not been shown. Further, WacA and AqpA are expressed at the late multicellular stage and in spores but not in amoebae. We cloned a novel AQP, AqpB, from amoeboidal D. discoideum cells. Wild-type AqpB was impermeable to water, glycerol, and urea when expressed in Xenopus laevis oocytes. Neither stepwise truncation of the N terminus nor selected point mutations activated the water channel. However, mutational truncation by 12 amino acids of an extraordinary long intracellular loop induced water permeability of AqpB, hinting at a novel gating mechanism. This AqpB mutant was inhibited by mercuric chloride, confirming the presence of a cysteine residue in the selectivity filter as predicted by our structure model. We detected AqpB by Western blot analysis in a glycosylated and a non-glycosylated form throughout all developmental stages. When expressed in D. discoideum amoebae, AqpB-GFP fusion constructs localized to vacuolar structures, to the plasma membrane, and to lamellipodia-like membrane protrusions. We conclude that the localization pattern in conjunction with channel gating may be indicative of AqpB functions in osmoregulation as well as cell motility of D. discoideum.
KW  - Aquaporin
KW  - Cell Motility
KW  - Dictyostelium
KW  - Gating
KW  - Transport
KW  - Osmoregulation
Y1  - 2021
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/76659
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-766595
SN  - 0021-9258
VL  - 287.2012
IS  - 10
SP  - 7487
EP  - 7494
PB  - American Society for Biochemistry and Molecular Biology Publications
CY  - Bethesda, Md
ER  -