14-3-3 proteins promote synaptic localization of N-methyl d-aspartate receptors (NMDARs) in mouse hippocampal and cortical neurons

One of the core pathogenic mechanisms for schizophrenia is believed to be dysfunction in glutamatergic synaptic transmissions, particularly hypofunction of N-methyl d-aspartate receptors (NMDARs). Previously we showed that 14-3-3 functional knockout mice exhibit schizophrenia-associated behaviors accompanied by reduced synaptic NMDARs in forebrain excitatory neurons. To investigate how 14-3-3 proteins regulate synaptic localization of NMDARs, here we examined changes in levels of synaptic NMDARs upon 14-3-3 inhibition in primary neurons. Expression of 14-3-3 protein inhibitor (difopein) in primary glutamatergic cortical and hippocampal neurons resulted in lower number of synaptic puncta containing NMDARs, including the GluN1, GluN2A, or GluN2B subunits. In heterologous cells, 14-3-3 proteins enhanced surface expression of these NMDAR subunits. Furthermore, we identified that 14-3-3ζ and ε isoforms interact with NMDARs via binding to GluN2A and GluN2B subunits. Taken together, our results demonstrate that 14-3-3 proteins play a critical role in NMDAR synaptic trafficking by promoting surface delivery of NMDAR subunits GluN1, GluN2A, and GluN2B. As NMDAR hypofunctionality is known to act as a convergence point for progression of symptoms of schizophrenia, further studies on these signaling pathways may help understand how dysfunction of 14-3-3 proteins can cause NMDAR hypofunctionality and lead to schizophrenia-associated behaviors.

Culinary Properties of Raw Versus Conventional Soy Sauce during Tuna Preparation

Soy sauce is a traditional Japanese seasoning made from fermented soybeans. As global demand grows, identifying novel soy sauce applications and benefits must become a priority. While conventional soy sauce undergoes heat-sterilization, filter-sterilization produces a lighter-colored (raw) soy sauce with preserved mold enzyme activities. As the impact of raw soy sauce during food (especially seafood) preparation remains unstudied, the present study compared the differential impact of raw and conventional soy sauce on tuna culinary properties. First, soy sauce color and protease activity were assessed. Next, tuna was marinated in soy sauce and non-alcoholic mirin for 0, 10, 35, or 60 min. Finally, marinated tuna properties (mass, salt content, surface salt penetration, color, rupture load, surface wetness, and protein content) were objectively assessed, and subjective sensory evaluation (appearance, aroma, wetness, softness, saltiness, umami, and overall taste) was performed by a blinded panel. Findings confirmed the lighter color of and the preservation of protease activity in raw soy sauce. Raw soy sauce significantly enhanced surface tenderization, salt penetration, and wetness, while both soy sauces increased surface firmness via salt-induced dehydration. Respondents significantly preferred the appearance and saltiness level of raw soy sauce-marinated tuna, and the umami and overall taste of tuna marinated in raw soy sauce for 60 min. The findings of this study, to our knowledge, demonstrate for the first time the potential culinary superiority of raw soy sauce in certain applications, and support future research to further define such applications.