SUMMARY The positioning of lysosomes within the cytoplasm is emerging as a critical determinant of many lysosomal functions. Here we report the identification of a multi-subunit complex named BORC that regulates lysosome positioning. BORC comprises eight subunits, some of which are shared with the BLOC-1 complex involved in the biogenesis of lysosome-related organelles, and the others of which are products of previously uncharacterized open reading frames. BORC associates peripherally with the lysosomal membrane, where it functions to recruit the small GTPase Arl8. This initiates a chain of interactions that promotes the Kinesin-1-dependent movement of lysosomes toward the plus ends of microtubules in the peripheral cytoplasm. Interference with BORC or other components of this pathway results in collapse of the lysosomal population into the pericentriolar region. In turn, this causes reduced cell spreading and migration, highlighting the importance of BORC-dependent centrifugal transport for non-degradative functions of lysosomes.

Here we present an evaluation of the binding affinity prediction accuracy of the free energy calculation method FEP+ on internal active drug discovery projects and on a large new public benchmark set. File list (3) download file view on ChemRxiv manuscript.pdf (4.23 MiB) download file view on ChemRxiv supplementary.pdf (0.92 MiB) download file view on ChemRxiv tables.zip (5.99 KiB)

In Saccharomyces cerevisiae, the synthesis of chitin is temporally and spatially regulated through the transport of Chs3p (chitin synthase III) to the plasma membrane in the bud neck region. Traffic of Chs3p from the trans‐Golgi network (TGN)/early endosome to the plasma membrane requires the function of Chs5p and Chs6p. Chs6p belongs to a family of four proteins that we have named ChAPs for Chs5p‐Arf1p‐binding Proteins. Here, we show that all ChAPs physically interact not only with Chs5p but also with the small GTPase Arf1p. A short sequence at the C‐terminus of the ChAPs is required for protein function and the ability to bind to Chs5p. Simultaneous disruption of two members, Δbud7 and Δbch1, phenocopies a Δchs6 or Δchs5 deletion with respect to Chs3p transport. Moreover, the ChAPs interact with each other and can form complexes. In addition, they are all at least partially localized to the TGN in a Chs5p‐dependent manner. Most importantly, several ChAPs can interact physically with Chs3p. We propose that the ChAPs facilitate export of cargo out of the Golgi.

Recycling of endocytic receptors to the cell surface involves passage through a series of membrane-bound compartments by mechanisms that are poorly understood. In particular, it is unknown if endocytic recycling requires the function of multisubunit tethering complexes, as is the case for other intracellular trafficking pathways. Herein we describe a tethering complex named Endosome-Associated Recycling Protein (EARP) that is structurally related to the previously described Golgi-Associated Retrograde Protein (GARP) complex. Both complexes share the Ang2, Vps52 and Vps53 subunits, but EARP comprises an uncharacterized protein, Syndetin, in place of the Vps54 subunit of GARP. This change determines differential localization of EARP to recycling endosomes and GARP to the Golgi complex. EARP interacts with the target-SNARE Syntaxin 6 and various cognate SNAREs. Depletion of Syndetin or Syntaxin 6 delays recycling of internalized transferrin to the cell surface. These findings implicate EARP in canonical membrane-fusion events in the process of endocytic recycling.