title: Effect of D-serine on spermatogenesis and extracellular signal-regulated protein kinase (ERK) phosphorylation in the testis of the silkworm, Bombyx mori.
abstract: Although the pupae and larvae of Bombyx mori possess especially large amounts of free d-serine, the physiological role of the amino acid in the silkworm is unknown. We investigated the effect of d-serine on spermatogenesis. A lowered d-serine level throughout larval development caused a delay in spermatogenesis and resulted in reduced numbers of eupyrene sperm. Administration of d-serine transiently increased the activation of extracellular signal-regulated protein kinase1/2 (ERK1/2; hereafter, ERK) by approximately 25% in the testis of day 3 fifth instar larvae. l-Serine had no effect on ERK activation, and other organs did not respond to d-serine. The effect of d-serine on ERK activation was confirmed by administering d-serine dehydratase, an enzyme that specifically degrades d-serine, and the enzyme's inhibitor, hydroxylamine. ERK phosphorylation in the testis was significantly inhibited by Go6983 and U0126, inhibitors of protein kinase C (PKC) and mitogen-associated protein kinase kinase 1/2 (MEK), respectively, but not by H-89, a protein kinase A (PKA) inhibitor, indicating that ERK was activated in the testis via PKC and MEK but not via PKA. The inhibition of ERK phosphorylation by Go6983 or U0126 was reduced by 20-30% by d-serine. Roughly 30% of c-Raf phosphorylation at an inhibitory site (Ser259) was decreased by the addition of d-serine. These results suggest that d-serine activates ERK in the testis of silkworms through a pathway including c-Raf but not PKC or MEK. Immunohistochemistry confirmed d-serine-induced ERK phosphorylation in the testis and revealed the presence of phospho-ERK in the nuclei of spermatocytes and spermatids.
authors: Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, Chiyoda-Ward, Tokyo 101-8308, Japan.
authors: Chihiro
authors: C
authors: Suzuki
authors: Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, Chiyoda-Ward, Tokyo 101-8308, Japan.
authors: Minoru
authors: M
authors: Tanigawa
authors: Department of Biochemistry and Molecular Biology, Shiga University of Medical Science, Ohtsu, Shiga 520-2192, Japan.
authors: Hiroyuki
authors: H
authors: Tanaka
authors: Department of Biochemistry and Molecular Biology, Shiga University of Medical Science, Ohtsu, Shiga 520-2192, Japan.
authors: Kihachiro
authors: K
authors: Horiike
authors: Department of Applied Biology, Faculty of Textile Science and Technology, Shinshu University, Ueda, Nagano 386-8567, Japan.
authors: Rensuke
authors: R
authors: Kanekatsu
authors: Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, Chiyoda-Ward, Tokyo 101-8308, Japan.
authors: Miki
authors: M
authors: Tojo
authors: Department of Materials and Applied Chemistry, College of Science and Technology, Nihon University, Chiyoda-Ward, Tokyo 101-8308, Japan. Electronic address: ocean_nagata@axel.ocn.ne.jp.
authors: Yoko
authors: Y
authors: Nagata
mesh_terms: D000818:Animals; D012831:Bombyx / Q000201:enzymology* / Q000254:growth & development*; D004791:Enzyme Inhibitors; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology*; D006836:Hydro-Lyases; D007814:Larva / Q000201:enzymology* / Q000254:growth & development*; D008297:Male; D020928:Mitogen-Activated Protein Kinases; D010766:Phosphorylation; D011494:Protein Kinases / Q000502:physiology*; D012694:Serine / Q000502:physiology*; D015398:Signal Transduction; D013091:Spermatogenesis / Q000502:physiology*; D013737:Testis / Q000201:enzymology / Q000254:growth & development*
chemical_list: D004791:Enzyme Inhibitors; D012694:Serine; D011494:Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D020928:Mitogen-Activated Protein Kinases; D006836:Hydro-Lyases; C101950:D-serine dehydratase
keywords: ERK; Signal transduction; Silkworm; Spermatogenesis; Testis; d-Serine