Ikaga R, Namekata I, Kotiadis VN, Ogawa H, Duchen MR, Tanaka H, Iida-Tanaka N. Knockdown of aquaporin-8 induces mitochondrial dysfunction in 3T3-L1 cells.
Biochem Biophys Rep 2015;
4:187-195. [PMID:
29124204 PMCID:
PMC5668916 DOI:
10.1016/j.bbrep.2015.09.009]
[Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 09/03/2015] [Accepted: 09/15/2015] [Indexed: 01/24/2023] Open
Abstract
Background
Aquaporin-8 (AQP8), a member of the aquaporin water channel family, is expressed in various tissue and cells, including liver, testis, and pancreas. AQP8 appears to have functions on the plasma membrane and/or on the mitochondrial inner membrane. Mitochondrial AQP8 with permeability for water, H2O2 and NH3 has been expected to have important role in various cells, but its information is limited to a few tissues and cells including liver and kidney. In the present study, we found that AQP8 was expressed in the mitochondria in mouse adipose tissues and 3T3-L1 preadipocytes, and investigated its role by suppressing its gene expression.
Methods
AQP8-knocked down (shAQP8) cells were established using a vector expressing short hairpin RNA. Cellular localization of AQP8 was examined by western blotting and immunocytochemistry. Mitochondrial function was assessed by measuring mitochondrial membrane potential, oxygen consumption and ATP level measurements.
Results
In 3T3-L1 cells, AQP8 was expressed in the mitochondria. In shAQP8 cells, mRNA and protein levels of AQP8 were decreased by about 75%. The shAQP8 showed reduced activities of complex IV and ATP synthase; it is probable that the impaired mitochondrial water handling in shAQP8 caused suppression of the electron transport and ADP phosphorylation through inhibition of the two steps which yield water. The reduced activities of the last two steps of oxidative phosphorylation in shAQP8 cause low routine and maximum capacity of respiration and mitochondrial hyperpolarization.
Conclusion
Mitochondrial AQP8 contributes to mitochondrial respiratory function probably through maintenance of water homeostasis.
General significance
The AQP8-knocked down cells we established provides a model system for the studies on the relationships between water homeostasis and mitochondrial function.
AQP8 was expressed in mouse adipose tissues and 3T3–L1 preadipocytes.
AQP8 was localized in mitochondria in 3T3–L1 cells.
Knockdown of AQP8 lowered routine and maximum capacity of mitochondrial respiration.
Knockdown of AQP8 reduced activities of complex IV and ATP synthase in mitochondria.
AQP8 contributes to maintain mitochondrial respirationprobably via water excretion.
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