ARS | Publication request: Hormone signaling linked to silkmoth sex pheromone biosynthesis involves Ca2+/calmodulin-dependent protein kinase II-mediated phosphorylation of the insect PAT family protein Bombyx mori lipid storage droplet protein-1(BmLsd)

Submitted to: Journal of Biological Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 11, 2011
Publication Date: July 8, 2011
Citation: Ohnishi, A., Hull, J.J., Kaji, M., Hashimoto, K., Lee, J., Tsuneizumi, K., Suzuki, T., Dohmae, N., Matsumoto, S. 2011. Hormone signaling linked to silkmoth sex pheromone biosynthesis involves Ca2+/calmodulin-dependent protein kinase II-mediated phosphorylation of the insect PAT family protein Bombyx mori lipid storage droplet protein-1(BmLsd). Journal of Biological Chemistry. vol. 286, no. 27, pp. 24101-24112.

Interpretive Summary: The mating behaviors of many lepidopteran pests are stimulated by sex pheromones. Consequently, targeted disruption of sex pheromone production pathways has the potential to augment, or even displace, current pest eradication programs. To achieve this goal, we first need a clear understanding of how sex pheromone pathways are regulated. In the silkmoth, Bombyx mori, fatty-acid sex pheromone precursors are stored in cytosolic lipid droplets waiting to be released into the pheromone biosynthetic pathway in response to the hormonal signal of pheromone biosynthesis activating neuropeptide (PBAN). The current paper describes work using molecular cloning techniques, anti-phospho amino acid Western blotting, and RNA interference-mediated knockdown of target genes via injected double-stranded RNAs to demonstrate that a recently identified protein, Bombyx mori lipid storage droplet protein-1, plays a crucial role in liberating these fatty-acid precursors in response to PBAN. Furthermore, the paper shows that BmLspd-1 activation is linked to phosphorylation by a specific kinase, calmodulin kinase II.

Technical Abstract: The structurally-related members of the PAT family of proteins, which are so name based on similarity amongst perilipin, adipophilin/adipocyte differentiation-related protein (ADRP), and tail-interacting protein of 47 kilodaltons (TIP47), are cytoplasmic lipid droplet (LD)-associated proteins characterized by an N-terminal ~100 residue sequence. In mammalian adipocytes, the PAT family protein perilipin plays an essential role in catecholamine-regulated triacylglycerol (TAG) lipolysis. Similar to mammalian adipocytes, pheromone gland (PG) cells of the silkmoth, Bombyx mori, accumulate cytoplasmic LDs and undergo TAG lipolysis, which releases the sex pheromone precursor fatty acids for pheromonogenesis and is triggered by a neurohormone termed pheromone biosynthesis activating neuropeptide (PBAN). PBAN exerts its physiological function via the PG cell-surface PBAN receptor (PBANR), a G protein-coupled receptor (GPCR) that belongs to the neuromedin U receptor family. The PBANR-mediated signal is transmitted via a canonical store-operated channel (SOC) activation pathway utilizing Gq-mediated phospholipase C (PLC) activation (Hull et al. (2007) Biosci. Biotechnol. Biochem. 71, 1993–2001; (2009) J. Biol. Chem. 284, 31200–31213; (2010) Insect Mol. Biol. in press). Little, however, is known about the molecular components regulating TAG lipolysis. In the current study, we found that an insect PAT family protein named B. mori lipid storage droplet protein-1 (BmLsd1) is predominantly expressed in the PG during pheromonogenesis and that it plays an essential role in pheromone production. Furthermore, BmLsd1 activation is dependent on B. mori Ca2+/calmodulin (CaM)-dependent protein kinase II (BmCaMKII) mediated phosphorylation in response to PBAN stimulation