HIGHLIGHTS from MBoC

The Editorial Board of Molecular Biology of the Cell has highlighted the following articles from the February and March 2016 issues. From among the many fine articles in the journal, the Board selects for these Highlights articles that are of broad interest and significantly advance knowledge or provide new concepts or approaches that extend our understanding.

 

Composite of super-resolution images of three vacuoles containing Toxoplasma gondii, ordered from early (left) to late (right) stage of daughter assembly. The cortical microtubules of the mother and the daughters as well as the mitotic spindle are highlighted by TLAP4 tagged with a green fluorescent protein (blue) and ectopically expressed from a constitutive promoter. The basal complexes of the mother and the daughters as well as a structure associated with the spindle pole are labeled by MORN1 tagged with a red fluorescent protein (red) and ectopically expressed from a constitutive promoter. In their paper in the February 1, 2016, issue (Mol. Biol. Cell 27, 549–571) Liu, He, et al. define differential localization of associated proteins in the microtubule cytoskeleton of T. gondii, explore the mechanism of specific targeting, and investigate the function of these proteins in stabilizing the cortical microtubules. (Image: Jun Liu and Ke Hu, Indiana University)

Composite of super-resolution images of three vacuoles containing Toxoplasma gondii, ordered from early (left) to late (right) stage of daughter assembly. The cortical microtubules of the mother and the daughters as well as the mitotic spindle are highlighted by TLAP4 tagged with a green fluorescent protein (blue) and ectopically expressed from a constitutive promoter. The basal complexes of the mother and the daughters as well as a structure associated with the spindle pole are labeled by MORN1 tagged with a red fluorescent protein (red) and ectopically expressed from a constitutive promoter. In their paper in the February 1, 2016, issue (Mol. Biol. Cell 27, 549–571) Liu, He, et al. define differential localization of associated proteins in the microtubule cytoskeleton of T. gondii, explore the mechanism of specific targeting, and investigate the function of these proteins in stabilizing the cortical microtubules. (Image: Jun Liu and Ke Hu, Indiana University)


APC binds the Miro/Milton motor complex to stimulate transport of mitochondria to the plasma membrane

Kate M. Mills, Mariana G. Brocardo, and Beric R. Henderson
The role of adenomatous polyposis coli (APC) tumor suppressor at mitochondria is unclear. We show that APC associates with the Miro/Milton/kinesin complex to stimulate anterograde transport of mitochondria. This identifies the first regulatory role of APC in organelle transport. APC cancer mutations block this activity.
Mol. Biol. Cell 27 (3), 466–482

The alternate AP-1 adaptor subunit Apm2 interacts with the Mil1 regulatory protein and confers differential cargo sorting
Shawn T. Whitfield, Helen E. Burston, Björn D. M. Bean, Nandini Raghuram, Lymarie Maldonado-Báez, Michael Davey, Beverly Wendland, and Elizabeth Conibear
Adaptor complexes are important for cargo sorting in clathrin-coated vesicles. The µ adaptor subunits Apm1 and Apm2 create functionally distinct versions of the yeast AP-1 complex. A novel regulatory protein is identified that selectively binds Apm2-containing complexes and contributes to their membrane recruitment.
Mol. Biol. Cell 27 (3), 588–598

The casein kinases Yck1p and Yck2p act in the secretory pathway, in part, by regulating the Rab exchange factor Sec2p
Danièle Stalder and Peter J. Novick
Sec2p is phosphorylated by the redundant casein kinases Yck1p and Yck2p. This promotes the interaction of Sec2p with the downstream effector, Sec15p, and contributes to Sec2p localization and function. Phosphorylation requires prior association of Sec2p with vesicles and reduction of the inhibitory Golgi lipid PI(4)P from the vesicle membrane.
Mol. Biol. Cell 27 (4), 686–701

Functional analysis of the interface between the tandem C2 domains of synaptotagmin-1
Chantell S. Evans, Zixuan He, Hua Bai, Xiaochu Lou, Pia Jeggle, R. Bryan Sutton, J. Michael Edwardson, and Edwin R. Chapman
Synaptotagmin (syt)-1 is a Ca2+ sensor that triggers rapid synaptic vesicle exocytosis. Mutations that disrupt physical interactions between the tandem Ca2+-sensing modules (C2 domains) of syt-1 disrupt regulated membrane fusion in reconstituted fusion reactions and in neurons. Hence contacts between these domains are important for function.
Mol. Biol. Cell 27 (6), 979–989

Small G-proteins are molecular switches that signal to the actin cytoskeleton to control the shape and movement of cells and their organelles. In the article in the March 15, 2016, issue (Mol. Biol. Cell 27, 967–978), Russo et al. report that the small G-protein Rab1 binds to the actin nucleation factor WHAMM to stimulate the tubulation of endomembranes. Rab1 is able to recruit WHAMM to membranes in cells, but unexpectedly limits its actin nucleation activity in vitro. This image depicts numerous tubular membranes radiating from the center of a cell co-expressing fluorescently tagged versions of Rab1 (red) and WHAMM (green). Actin filaments are shown in in magenta and nuclear DNA in blue. (Image: Ken Campellone, University of Connecticut)

Small G-proteins are molecular switches that signal to the actin cytoskeleton to control the shape and movement of cells and their organelles. In the article in the March 15, 2016, issue (Mol. Biol. Cell 27, 967–978), Russo et al. report that the small G-protein Rab1 binds to the actin nucleation factor WHAMM to stimulate the tubulation of endomembranes. Rab1 is able to recruit WHAMM to membranes in cells, but unexpectedly limits its actin nucleation activity in vitro. This image depicts numerous tubular membranes radiating from the center of a cell co-expressing fluorescently tagged versions of Rab1 (red) and WHAMM (green). Actin filaments are shown in in magenta and nuclear DNA in blue. (Image: Ken Campellone, University of Connecticut)

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