Author Archives: Max Ferrin

Paper by Ross, Julian, and Paul on endocytic maturation published in JCB

Congratulations to Ross, Julian, and Paul on their paper “Spatial regulation of clathrin-mediated endocytosis through position-dependent site maturation” now published in JCB.

Cargo regulates the transition between two quantitatively distinguishable phases of endocytosis. (A) Revised timeline for the CME pathway indicating the proposed temporal location of the cargo checkpoint. Proteins upstream and downstream of the checkpoint are listed under each phase. (B) Schematic cartoon illustrating the proposed mechanism leading to polarized endocytosis in budding yeast. In highly polarized cells, endocytic cargos (black arrows) are delivered primarily to the growing bud by exocytosis (gray arrows), locally accelerating the transition from the initiation and cargo-collection phase of CME (green spots) into the internalization phase (magenta spots). As exocytosis becomes depolarized later in the cell cycle, cargos are more plentiful across the plasma membrane, leading to global acceleration of maturation through the cargo checkpoint.

Paper by Michelle on a novel function of CDC42 published in JCB

Congratulations to Michelle on her paper “Cdc42 GTPase regulates ESCRTs in nuclear envelope sealing and ER remodeling ” now published in JCB.

Cdc42, ESCRT-III, and Heh2 mutants share a leaky nucleus phenotype. (A) In normal cells, Heh2, Chm7, and Snf7 function at holes in the nuclear envelope to carry out annular fusion. ESCRT-III polymers are disassembled by Vps4, and we propose that Cdc42 is involved in the disassembly step by either directly contributing to Snf7 disassembly, activating Vps4 function, or cooperating with Vps4. (B) Mutants lacking components directly involved in annular fusion have holes in their nuclear envelopes left by nuclear fusion and ER fission events. (C) Cells lacking Vps4 and normal Cdc42 have unregulated ESCRT activity at the nuclear envelope. This causes the formation of nuclear karmallae and large holes in the nuclear envelope, leading to a defect in proper nucleo-cytoplasmic partitioning. ONM, outer nuclear membrane; INM, inner nuclear membrane.

Paper by Yidi Sun on budding vs. fission yeast CME now published in eLife

Congratulations to Yidi, her former undergraduate Tommy, Joh, Charlotte, and collaborators in the Xu Lab and Pollard Lab on their new paper “Direct comparison of clathrin-mediated endocytosis in budding and fission yeast reveals conserved and evolvable features” now published at eLife!

Comparison of endocytic vesicle formation in fission and budding yeast. Timeline and summary of the average molecule numbers for indicated coat proteins and actin machinery components in fission (A) and budding yeast (B) endocytosis. Scission occurs at the time 0. Steps (I) through (V) represent the full process from membrane invagination initiation to vesicle scission. See text (last section in Discussion) for detailed key similarities and differences in fission yeast and budding yeast in terms of protein numbers, architecture and function of the endocytic coat and associated actin machinery.