The immunological synapse (IS) formed at the interface between T cells and antigen-presenting cells represents a hallmark of initiation of acquired immunity. T cell activation is initiated at T cell receptor (TCR) microclusters (MCs), in which TCRs and signaling molecules assemble at the interface before IS formation. We found that each TCR-MC was transiently bordered by a ring structure made of integrin and focal adhesion molecules in the early phase of activation, which is similar in structure to the IS in microscale. The micro–adhesion ring is composed of LFA-1, focal adhesion molecules paxillin and Pyk2, and myosin II (MyoII) and is supported by F-actin core and MyoII activity through LFA-1 outside-in signals. The formation of the micro–adhesion ring was transient but especially sustained upon weak TCR stimulation to recruit linker for activation of T cells (LAT) and SLP76. Perturbation of the micro–adhesion ring induced impairment of TCR-MC development and resulted in impaired cellular signaling and cell functions. Thus, the synapse-like structure composed of the core TCR-MC and surrounding micro–adhesion ring is a critical structure for initial T cell activation through integrin outside-in signals.

In macroautophagy, cellular components are sequestered within autophagosomes and transported to lysosomes/vacuoles for degradation. Although phosphatidylinositol 3-kinase complex I (PI3KCI) plays a pivotal role in the regulation of autophagosome biogenesis, little is known about how this complex localizes to the pre-autophagosomal structure (PAS). In Saccharomyces cerevisiae, PI3KCI is composed of PI3K Vps34 and conserved subunits Vps15, Vps30, Atg14, and Atg38. In this study, we discover that PI3KCI interacts with the vacuolar membrane anchor Vac8, the PAS scaffold Atg1 complex, and the pre-autophagosomal vesicle component Atg9 via the Atg14 C-terminal region, the Atg38 C-terminal region, and the Vps30 BARA domain, respectively. While the Atg14–Vac8 interaction is constitutive, the Atg38–Atg1 complex interaction and the Vps30–Atg9 interaction are enhanced upon macroautophagy induction depending on Atg1 kinase activity. These interactions cooperate to target PI3KCI to the PAS. These findings provide a molecular basis for PAS targeting of PI3KCI during autophagosome biogenesis.

Abnormal hepatic insulin signaling is a cause or consequence of hepatic steatosis. DPP-4 inhibitors might be protective against fatty liver. We previously reported that the systemic inhibition of insulin receptor (IR) and IGF-1 receptor (IGF1R) by the administration of OSI-906 (linsitinib), a dual IR/IGF1R inhibitor, induced glucose intolerance, hepatic steatosis, and lipoatrophy in mice. In the present study, we investigated the effects of a DPP-4 inhibitor, linagliptin, on hepatic steatosis in OSI-906-treated mice. Unlike high-fat diet-induced hepatic steatosis, OSI-906-induced hepatic steatosis is not characterized by elevations in inflammatory responses or oxidative stress levels. Linagliptin improved OSI-906-induced hepatic steatosis via an insulin-signaling-independent pathway, without altering glucose levels, free fatty acid levels, gluconeogenic gene expressions in the liver, or visceral fat atrophy. Hepatic quantitative proteomic and phosphoproteomic analyses revealed that perilipin-2 (PLIN2), major urinary protein 20 (MUP20), cytochrome P450 2b10 (CYP2B10), and nicotinamide N-methyltransferase (NNMT) are possibly involved in the process of the amelioration of hepatic steatosis by linagliptin. Thus, linagliptin improved hepatic steatosis induced by IR and IGF1R inhibition via a previously unknown mechanism that did not involve gluconeogenesis, lipogenesis, or inflammation, suggesting the non-canonical actions of DPP-4 inhibitors in the treatment of hepatic steatosis under insulin-resistant conditions.

The molecular mechanisms associated with spaceflight‐induced biological adaptations that may affect many healthy tissue functions remain poorly understood. In this study, we analyzed temporal changes in the serum proteome of six astronauts during prolonged spaceflight missions using quantitative comprehensive proteome analysis performed with the data‐independent acquisition method of mass spectrometry (DIA‐MS). All six astronauts participated in a spaceflight mission for approximately 6 months and showed a decreasing trend in T‐scores at almost all sites where dual‐energy X‐ray absorptiometry scans were performed. DIA‐MS successfully identified 624 nonredundant proteins in sera and further quantitative analysis for each sampling point provided information on serum protein profiles closely related to several time points before (pre‐), during (in‐), and after (post‐) spaceflight. Changes in serum protein levels between spaceflight and on the ground suggest that abnormalities in bone metabolism are induced in astronauts during spaceflight. Furthermore, changes in the proteomic profile occurring during spaceflight suggest that serum levels of bone metabolism‐related proteins, namely ALPL, COL1A1, SPP1, and POSTN, could serve as highly responsive indicators of bone metabolism status in spaceflight missions. This study will allow us to accelerate research to improve our understanding of the molecular mechanisms of biological adaptations associated with prolonged spaceflight.