CC2D1A Is a Regulator of ESCRT-III CHMP4B

Abstract

Endosomal sorting complexes required for transport (ESCRT) regulate diverse processes ranging from receptor sorting at endosomes to distinct steps in cell division and budding of some enveloped viruses. Common to all processes is the membrane recruitment of ESCRT-III that leads to membrane fission. Here, we show that CC2D1A is a novel regulator of ESCRT-III CHMP4B function. We demonstrate that CHMP4B interacts directly with CC2D1A and CC2D1B with nanomolar affinity by forming a 1:1 complex. Deletion mapping revealed a minimal CC2D1A-CHMP4B binding construct, which includes a short linear sequence within the third DM14 domain of CC2D1A. The CC2D1A binding site on CHMP4B was mapped to the N-terminal helical hairpin. Based on a crystal structure of the CHMP4B helical hairpin two surface patches were identified that interfere with CC2D1A interaction as determined by surface plasmon resonance. Introducing these mutations into a C-terminal truncation of CHMP4B that exerts a potent dominant negative effect on HIV-1 budding, revealed that one of the mutants lost this effect completely. This suggests that the identified CC2D1A binding surface might be required for CHMP4B polymerization, which is consistent with the finding that CC2D1A binding to CHMP4B prevents CHMP4B polymerization in vitro. Thus, CC2D1A might act as a negative regulator of CHMP4B function.

Activation of Notch in lgd mutant cells requires the fusion of late endosomes with the lysosome

“…A similar interaction has been reported between the mammalian orthologues of Lgd interact and the orthologues of Shrub, CHMP4a, b, c (Martinelli et al, 2012;Usami et al, 2012). Moreover, in vitro experiments suggest that Lgd1 and Lgd2 can influence the polymerisation of CHMP proteins (Martinelli et al, 2012). We therefore favour the possibility that upon loss of lgd function, Notch is inefficiently incorporated into the ILVs due to a reduction, but not abolishment in the activity of shrub.…”

“…We have recently shown that Lgd physically interacts with Shrub and is required for its full function (figure 9A, Troost et al, 2012). A similar interaction has been reported between the mammalian orthologues of Lgd interact and the orthologues of Shrub, CHMP4a, b, c (Martinelli et al, 2012;Usami et al, 2012). Moreover, in vitro experiments suggest that Lgd1 and Lgd2 can influence the polymerisation of CHMP proteins (Martinelli et al, 2012).…”

TBK1-associated Protein in Endolysosomes (TAPE)/CC2D1A Is a Key Regulator Linking RIG-I-like Receptors to Antiviral Immunity

“…S1), suggesting a link between the role of TAPE in endosomal trafficking and RLR signaling. Interestingly, recent studies indicated that TAPE/CC2D1A binds to and negatively regulates CHMP4B, a component of the endosomal sorting complexes required for transport (ESCRT) pathway, leading to the inhibition of HIV-1 budding (21,22). These findings further support the importance of TAPE in regulating the endolysosomal compartments.…”

Molecular Mechanisms of the Membrane Sculpting ESCRT Pathway

“…Numerous electron micrographs exist for ESCRT-III assemblies, but these cannot reveal details like protein -protein interfaces. Currently, crystal structures exist for portions of VPS24/CHMP3, SNF7/CHMP4, and IST1 (Muziol et al 2006;Bajorek et al 2009;Martinelli et al 2012). However, there are no structures of either full-length ESCRT-III subunits, or ESCRT-III hetero-oligomers.…”