Masaaki Yoshikawa

β-Lactotensin derived from bovine β-lactoglobulin exhibits anxiolytic-like activity as an agonist for neurotensin NTS2 receptor via activation of dopamine D1 receptor in mice

J. Neurochem. (2011) 119, 785–790.

Rapakinin, Arg–Ile–Tyr, derived from rapeseed napin, shows anti-opioid activity via the prostaglandin IP receptor followed by the cholecystokinin CCK2 receptor in mice

Rapakinin, Arg-Ile-Tyr, is a vasorelaxing, anti-hypertensive and anorexigenic peptide derived from rapeseed napin. In this study, we found that rapakinin intracerebroventricularly administered to mice inhibited the analgesic effect of morphine, evaluated by the tail-pinch test. The anti-opioid activity of rapakinin was blocked by LY225910, an antagonist of the cholecystokinin (CCK) CCK(2) receptor, but not by lorglumide, an antagonist of the CCK(1) receptor. The anti-opioid activity of rapakinin was also blocked by CAY10441, an antagonist of the prostaglandin (PG) IP receptor. These results suggest that the anti-opioid activity of rapakinin is mediated by the CCK(2) and IP receptors. The anti-opioid activity induced by ciprostene, an IP receptor agonist, was blocked by LY225910, while that of CCK-8 was not blocked by CAY10441. Thus, it is demonstrated that the CCK-CCK(2) system was activated downstream of the PGI(2)-IP receptor system. Taken together, rapakinin shows anti-opioid activity via the activation of the PGI(2)-IP receptor system followed by the CCK-CCK(2) receptor system.

Development of transgenic rice containing a mutated β subunit of soybean β-conglycinin for enhanced phagocytosis-stimulating activity.

Improving the nutraceutical value of rice would positively impact the health and well-being of rice consumers worldwide. Based on the three-dimensional structure of soybean beta-conglycinin, we designed a beta subunit with a strong phagocytosis-stimulating activity (mbeta subunit). Here, we describe the genetic modification and production of rice seeds containing the mbeta subunit as part of our aim to develop a food material that promotes human health. The mbeta subunit folded correctly and was accumulated in the protein body II of rice seeds at a level similar to wild-type beta subunit. Mutant beta subunit purified from transgenic rice seeds exhibited high phagocytosis-stimulating activity, demonstrating its potential value in enhancing the nutritional value of rice.

Seed Storage Proteins; Strategies for Developing Crops Promoting Human Health

Plant seeds contain high amounts of storage proteins. These are classified on basis of their solubility as water-soluble albumins, salt-soluble globulins, alcohol-soluble prolamins, and acidor alkaline-soluble glutelins (Osborne 1924, Utsumi, 1992). The compositions of seed storage proteins differ among plant species. For examples, monocot seeds contain mainly glutelins and prolamins (Ogawa et al., 1987; Li & Okita, 1993; Cagampang et al., 1966), whereas legume seeds contain mainly 7S/11S globulins (Utsumi, 1992). Rice is the staple food of approximately half of the population of the world. The major seed storage proteins of rice are glutelins and prolamin, similarly to the other monocots. The seed storage proteins present in rice, however, offer little significant benefit to human physiology. Therefore, improving the nutritional and physiological values of rice would be of benefit to the health of considerable numbers of people. A candidate protein that might be of interest in the context of improving the physiological values of rice is β-conglycinin. The seed storage protein of soybean, β-conglycinin, lowers plasma cholesterol and triglyceride levels in humans (Sirtori et al., 1995; Aoyama et al., 2001). Moreover, βconglycinin increases adiponectin levels and improves glucose tolerance (Tachibana et al., 2010). The α’ subunit of β-conglycinin has LDL-cholesterol-lowering activity (Sirtori and Lovati, 2001) and contains a phagocytosis-stimulating peptide (Tsuruki et al., 2003). Therefore, development of rice that can accumulate β-conglycinin should produce a staple food with several important physiological benefits to human health. β-Conglycinin has the trimeric structure common to 7S globulins of other plant species and is composed of three subunits, α, α’ and β. The α and α’ subunits contain an N-terminal extension in addition to a core region common to all the subunits (Maruyama et al., 1998, 2001 & 2004). The β subunit consists of only the core domain. The α and α’ subunits and the β subunit are synthesized on polysomes as preproand pre-forms, respectively. The signal peptides are co-translationally removed, the polypeptides are N-glycosylated with highmannose glycans and assemble into trimers in the ER (Yamauchi & Yamagishi, 1979; Utsumi, 1992). They are transported from the ER to the protein storage vacuoles through the Golgi apparatus (Mori et al., 2004). The pro regions of the α and α’ subunits are