title: Identification and lateral membrane localization of cyclin M3, likely to be involved in renal Mg2+ handling in seawater fish.
abstract: The kidney of marine teleosts is the major site of Mg(2+) excretion and produces urine with a high Mg(2+) concentration. However, the transporters involved in Mg(2+) excretion are poorly understood. The cyclin M (Cnnm; also known as ancient conserved domain protein) family comprises membrane proteins homologous to the bacterial Mg(2+) and Co(2+) efflux protein, CorC. To understand the molecular mechanism of Mg(2+) homeostasis in marine teleosts, we analyzed the expression of the Cnnm family genes in the seawater (SW) pufferfish, torafugu (Takifugu rubripes), and the closely related euryhaline species, mefugu (Takifugu obscurus). Database mining and phylogenetic analysis indicated that the Takifugu genome contains six members of the Cnnm family: two orthologs of Cnnm1, one of Cnnm2, one of Cnnm3, and two of Cnnm4. RT-PCR analyses indicated that Cnnm2, Cnnm3, and Cnnm4a are expressed in the kidney, whereas other members are mainly expressed in the brain. Renal expression of Cnnm3 was upregulated in SW mefugu, whereas renal expression of Cnnm2 was upregulated in freshwater (FW) mefugu. No significant difference was observed in renal expression of Cnnm4a between SW and FW mefugu. In situ hybridization and immunohistochemical analyses of the SW mefugu kidney revealed that Cnnm3 is expressed in the proximal tubule, and its product localizes to the lateral membrane. When Cnnm3 was expressed in Xenopus laevis oocytes, whole cellular Mg(2+) content and free intracellular Mg(2+) activity significantly decreased. These results suggest that Cnnm3 is involved in body fluid Mg(2+) homeostasis in marine teleosts.
authors: Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan;
authors: Zinia
authors: Z
authors: Islam
authors: Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan;
authors: Naoko
authors: N
authors: Hayashi
authors: Department of Physiology, Tokyo Medical University, Tokyo, Japan;
authors: Hana
authors: H
authors: Inoue
authors: Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan;
authors: Takahiro
authors: T
authors: Umezawa
authors: Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan;
authors: Yuuri
authors: Y
authors: Kimura
authors: Shimonoseki Marine Science Museum, Shimonoseki, Japan;
authors: Hiroyuki
authors: H
authors: Doi
authors: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota; Nephrology and Hypertension, Mayo Clinic College of Medicine, Rochester, Minnesota; and O'Brien Urology Research Center, Mayo Clinic College of Medicine, Rochester, Minnesota.
authors: Michael F
authors: MF
authors: Romero
authors: Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan;
authors: Shigehisa
authors: S
authors: Hirose
authors: Department of Biological Sciences, Tokyo Institute of Technology, Yokohama, Japan; Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota; akirkato@bio.titech.ac.jp.
authors: Akira
authors: A
authors: Kato
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D016678:Genome; D006706:Homeostasis / Q000502:physiology; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D053403:Lateral Line System / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D023741:Takifugu / Q000502:physiology*
chemical_list: D016213:Cyclins; D008274:Magnesium
keywords: Cnnm3; lateral membrane; magnesium homeostasis; marine teleost; proximal tubule