A protein-protein interaction map reveals that the Coxiella burnetii effector CirB inhibits host proteasome activity.

Coxiella burnetii is the etiological agent of the zoonotic disease Q fever, which is featured by its ability to replicate in acid vacuoles resembling the lysosomal network. One key virulence determinant of C. burnetii is the Dot/Icm system that transfers more than 150 effector proteins into host cells. These effectors function to construct the lysosome-like compartment permissive for bacterial replication, but the functions of most of these effectors remain elusive. In this study, we used an affinity tag purification mass spectrometry (AP-MS) approach to generate a C. burnetii-human protein-protein interaction (PPI) map involving 53 C. burnetii effectors and 3480 host proteins. This PPI map revealed that the C. burnetii effector CBU0425 (designated CirB) interacts with most subunits of the 20S core proteasome. We found that ectopically expressed CirB inhibits hydrolytic activity of the proteasome. In addition, overexpression of CirB in C. burnetii caused dramatic inhibition of proteasome activity in host cells, while knocking down CirB expression alleviated such inhibitory effects. Moreover, we showed that a region of CirB that spans residues 91-120 binds to the proteasome subunit PSMB5 (beta 5). Finally, PSMB5 knockdown promotes C. burnetii virulence, highlighting the importance of proteasome activity modulation during the course of C. burnetii infection.

The classical and potential novel healthy functions of rice bran protein and its hydrolysates.

Rice bran protein (RBP) is a plant protein obtained from rice bran, a byproduct produced during rice milling process. It has been proved to be a high quality protein due to containing all of the essential amino acids and the content closing to the FAO/WHO recommended ideal pattern. Recent studies indicated that RBP and rice bran protein hydrolysates (RBPH) served variety biological functions. In this review, we summarized the classical functions of RBP and RBPH mediating antioxidant activity, chronic diseases prevention (such as antihypertensive effect, anti-diabetic effect, cholesterol-lowering activity), and anti-cancer effect. We also proposed their potential novel functions on anti-obesity effect, attenuating sarcopenia, promoting wound healing. Furthermore, the potential benefit to coronavirus disease 2019 (COVID-19) patients was put forward, which might provide new strategy for development and utilization of RBP and RBPH.