TRIM proteins regulate autophagy: TRIM5 is a selective autophagy receptor mediating HIV-1 restriction

The tripartite motif protein family (TRIM) constitutes a class of immune-regulated proteins with antiviral, immune, cancer, and other properties reminiscent of those ascribed to autophagy. We show that TRIMs have dual roles in autophagy: as regulators and as cargo receptors. As regulators, TRIMs nucleate the core autophagy machinery by acting as platforms that assemble ULK1 and BECN1 into a functional complex in preparation for autophagy. TRIMs also act as novel selective autophagy receptors as exemplified by TRIM5/TRIM5 alpha, a known HIV-1 restriction factor with a hitherto poorly defined mode of action. TRIM5 recognizes and targets HIV-1 for autophagic destruction. TRIM5 interactions with mammalian Atg8 proteins are required for this effector function. This establishes TRIM family members as regulators of autophagy, explains the antiretroviral mechanism of TRIM5, and defines a new basis for selective autophagy.