title: Aquaporin-3 re-expression induces differentiation in a phospholipase D2-dependent manner in aquaporin-3-knockout mouse keratinocytes.
abstract: Aquaporin-3 (AQP3) is a water and glycerol channel expressed in epidermal keratinocytes. Despite many studies, controversy remains about the role of AQP3 in keratinocyte differentiation. Previously, our laboratory has shown co-localization of AQP3 and phospholipase D2 (PLD2) in caveolin-rich membrane microdomains. We hypothesized that AQP3 transports glycerol and "funnels" this primary alcohol to PLD2 to form a pro-differentiative signal, such that the action of AQP3 to induce differentiation should require PLD2. To test this idea, we re-expressed AQP3 in mouse keratinocytes derived from AQP3-knockout mice. The re-expression of AQP3, which increased [3H]glycerol uptake, also induced mRNA and protein expression of epidermal differentiation markers such as keratin 1, keratin 10, and loricrin, with or without the induction of differentiation by an elevated extracellular calcium concentration. Re-expression of AQP3 had no effect on the expression of the proliferation markers keratin 5 and cyclin D1. Furthermore, a selective inhibitor of PLD2, CAY10594, and a lipase-dead (LD) PLD2 mutant, but not a LD PLD1 mutant, significantly inhibited AQP3 re-expression-induced differentiation marker expression with calcium elevation, suggesting a role for PLD2 in this process. Thus, our results indicate that AQP3 has a pro-differentiative role in epidermal keratinocytes and that PLD2 activity is necessary for this effect.
authors.affiliation: Charlie Norwood VA Medical Center, Augusta, Georgia, USA; Department of Physiology, Georgia Regents University, Augusta, Georgia, USA; Section of Dermatology, Department of Medicine, Georgia Regents University, Augusta, Georgia, USA.
authors.forename: Vivek
authors.initials: V
authors.lastname: Choudhary
authors.affiliation: Charlie Norwood VA Medical Center, Augusta, Georgia, USA; Department of Physiology, Georgia Regents University, Augusta, Georgia, USA.
authors.forename: Lawrence O
authors.initials: LO
authors.lastname: Olala
authors.affiliation: Charlie Norwood VA Medical Center, Augusta, Georgia, USA; Department of Physiology, Georgia Regents University, Augusta, Georgia, USA.
authors.forename: Haixia
authors.initials: H
authors.lastname: Qin
authors.affiliation: Charlie Norwood VA Medical Center, Augusta, Georgia, USA; Department of Physiology, Georgia Regents University, Augusta, Georgia, USA.
authors.forename: Inas
authors.initials: I
authors.lastname: Helwa
authors.affiliation: Department of Physiology, Georgia Regents University, Augusta, Georgia, USA; School of Basic Medical Science, Shanghai University of Traditional Chinese Medicine, Shanghai, China.
authors.forename: Zhi-Qiang
authors.initials: ZQ
authors.lastname: Pan
authors.affiliation: Department of Physiology, Georgia Regents University, Augusta, Georgia, USA.
authors.forename: Ying-Ying
authors.initials: YY
authors.lastname: Tsai
authors.affiliation: Department of Pharmacology and Center for Developmental Genetics, Stony Brook University, Stony Brook, New York, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Frohman
authors.affiliation: Charlie Norwood VA Medical Center, Augusta, Georgia, USA; Department of Physiology, Georgia Regents University, Augusta, Georgia, USA.
authors.forename: Ismail
authors.initials: I
authors.lastname: Kaddour-Djebbar
authors.affiliation: Charlie Norwood VA Medical Center, Augusta, Georgia, USA; Department of Physiology, Georgia Regents University, Augusta, Georgia, USA; Section of Dermatology, Department of Medicine, Georgia Regents University, Augusta, Georgia, USA. Electronic address: WB@gru.edu.
authors.forename: Wendy B
authors.initials: WB
authors.lastname: Bollag
mesh_terms: D000818:Animals; D051400:Aquaporin 3 / Q000502:physiology*; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D015603:Keratinocytes / Q000166:cytology*; D051379:Mice; D018345:Mice, Knockout; D010739:Phospholipase D / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: C496028:Aqp3 protein, mouse; D051400:Aquaporin 3; C105606:phospholipase D2; D010739:Phospholipase D