Cell Biology

INPP5E regulates CD3ζ enrichment at the immune synapse by phosphoinositide distribution control

1. Tzu-Yuan Chiu
2. Fu-Hua Yang
3. Weng Man Chong
4. Hsing-Chen Tsai
5. Won-Jing Wang
6. Jung-Chi Liao

Reviewed by eLife

Disparate Bone Anabolic Cues Activate Bone Formation by Regulating the Rapid Lysosomal Degradation of Sclerostin Protein

1. Nicole R. Gould
2. Katrina M. Williams
3. Humberto C. Joca
4. Olivia M. Torre
5. James S. Lyons
6. Jenna M. Leser
7. Manasa P. Srikanth
8. Marcus Hughes
9. Ramzi J. Khairallah
10. Ricardo A. Feldman
11. Christopher W. Ward
12. Joseph P. Stains

• Curated by eLife

  Summary: The article by Gould et al breaks new ground by demonstrating a role for lysosomal-mediated degradation in the mechanosensitive repression of Sclerostin levels in bone. Though the post-translational repression of Sclerostin has long been apparent, no one has yet unraveled the mechanisms. Therefore, this discovery is important to the skeletal biology community - both because of the findings themselves, and because the conditions/models used by this team to make these discoveries will be useful for other investigators, including their ability to manipulate and observe the rapid lysosome-dependent control of Sclerostin levels in vitro and in vivo in response to PTH or mechanical stimulation. In addition to the importance within this field, the work has broad impact on multiple levels including a) the clinical relevance for understanding and potentially treating osteoporosis and the skeletal phenotypes in individuals with lysosomal disease, and b) the mechanoregulation of lysosomal function and its relationships to crinophagy, which has implications not only for the regulation of Sclerostin, but also for other factors in and beyond the skeleton (RANKL, insulin).

  Essential revisions:

  The study is elegantly designed, clearly communicated, and rigorously conducted. However, the reviewers require additional data to support the overall conclusion on the significance of lysosome-mediated degradation of sclerostin in skeletal biology. First, it is important to elaborate on what gives the authors confidence that the inhibitors were effective and act as expected throughout the study - but especially Bafilomycin A1 and Apocynin in vivo. If BafA1 and Apocynin treatment in vivo work as expected, they should prevent the rapid load-dependent repression of Sclerostin levels (shown in Figure 1D). Second, the author's demonstration of mechanical load-dependent changes in sclerostin localization in osteocytes lysosomes in vivo by immunohistochemistry would be important to support the in vivo relevance of this pathway in the acute regulation of sclerostin levels. While the western blotting of mechanically loaded mouse ulnas showing previously-undocumented acute reductions in lysate sclerostin levels is interesting, it is unclear if these changes are caused by mechanical loading-induced lysosomal function.

  Reviewer #1 and Reviewer #2 opted to reveal their name to the authors in the decision letter after review.

Reviewed by eLife

De Novo Lipid Labeling for Comprehensive Analysis of Subcellular Distribution and Trafficking in Live Cells

1. Jun Zhang
2. Jia Nie
3. Haoran Sun
4. John-Paul Andersen
5. Yuguang Shi

• Curated by eLife

  Summary: Zhang et al. describe an interesting method to label newly synthesized lipids with fluorescent fatty acids and track their movement in cells. All reviewers agreed that this could potentially be a useful tool. However, they all raised concerns regarding the rigor of the characterization of this methodology.

Reviewed by eLife

Flagellar energetics from high-resolution imaging of beating patterns in tethered mouse sperm

1. Ashwin Nandagiri
2. Avinash S. Gaikwad
3. David L. Potter
4. Reza Nosrati
5. Julio Soria
6. Moira K. O’Bryan
7. Sameer Jadhav
8. Ranganathan Prabhakar

Reviewed by eLife

LAP2alpha maintains a mobile and low assembly state of A-type lamins in the nuclear interior

1. Nana Naetar
2. Konstantina Georgiou
3. Christian Knapp
4. Irena Bronshtein
5. Elisabeth Zier
6. Petra Fichtinger
7. Thomas Dechat
8. Yuval Garini
9. Roland Foisner

• Curated by eLife

  Summary: This work builds on prior studies by the Foisner group that investigated the function(s) of the soluble A-type lamin binding protein, LAP2a. One of their prior observations using antibody labeling was that there appeared to be a depletion of the nucleoplasmic pool of A-type lamins in cells lacking LAP2a. In this manuscript, the authors employ CRISPR-Cas9 editing to develop new tools to investigate the attributes specific to nucleoplasmic versus lamina-integrated A-type lamins. Using this new approach (and comparing it with their prior observations), the authors hit upon a new model in which LAP2a influences the conformational state of A-type lamins, which in turn influences its detection by a commonly used antibody. This technical detail explains the new realization that nucleoplasmic lamin A persists in LAP2a-null cells, albeit in a different state. The authors provide evidence that LAP2a antagonizes stable lamin A filament assembly, that is absence leads to stabilized intranuclear lamin A assemblies, and that telomere mobility is negatively influenced by loss of LAP2a in a manner depending on the presence of lamin A/C. The authors' work further identifies two pathways by which nucleoplasmic lamins emerge, namely by 1) initial localization to the lamina followed by relocalization to the nucleoplasm, and 2) from the pool of mitotic lamins which are not associated to the lamina.

  Overall there was enthusiasm for the study, with the reviewers stating their appreciation for the author's mechanistic approach to studying lamin assembly state and the use of complementary cell biology/microscopy and biochemical approaches. The rigor of the science was also lauded, including inclusion of, for example, genome editing quality control measures. Taken together the reviewers felt that the findings provided a new perspective on how LAP2a influences the state of A-type lamins. As the impact of lamins on nuclear organization is critical for nuclear functions and important for nuclear integrity, these results are fundamental for the understanding of both lamin A/C and LAP2a.

Reviewed by eLife

The multi-scale architecture of mammalian sperm flagella and implications for ciliary motility

1. Miguel Ricardo Leung
2. Marc C. Roelofs
3. Ravi Teja Ravi
4. Paula Maitan
5. Min Zhang
6. Heiko Henning
7. Elizabeth G. Bromfield
8. Stuart C. Howes
9. Bart M. Gadella
10. Hermes Bloomfield-Gadêlha
11. Tzviya Zeev-Ben-Mordehai

Reviewed by Review Commons

Septins coordinate cell wall integrity and lipid metabolism in a sphingolipid-dependent process

1. Alexander Mela
2. Michelle Momany

Reviewed by Review Commons

Kinesin-4 KIF21B limits microtubule growth to allow rapid centrosome polarization in T cells

1. Peter Jan Hooikaas
2. Hugo G.J. Damstra
3. Oane J. Gros
4. Wilhelmina E. van Riel
5. Maud Martin
6. Yesper T.H. Smits
7. Jorg van Loosdregt
8. Lukas C. Kapitein
9. Florian Berger
10. Anna Akhmanova

• Curated by eLife

  Summary: This is a very interesting study addressing the question of microtubule cytoskeleton reorganization in the immunological synapse. Specifically, the work demonstrates the contribution of KIF21B for the control of the T cell microtubule (MT) network required for T cell polarization during immunological synapse formation. The authors use a variety of microscopy techniques, including expansion microscopy, controlled perturbations of the cell, and computer simulations to generate their results. The authors show that knockout of KIF21B results in longer MTs that result in an inability to polarise the MT network by a mechanism consistent with dynein motor function at the immunological synapse to capture long MTs and center the MT aster at the synapse. They use the Jurkat cell line, which is a classical model for this step in immune synapse function and fully appropriate. They show that KIF21B-GFP can rescue the knockout phenotype and then use this as a way to follow KIF12B dynamics in the Jurkat cells. KIF21B works by inducing pausing and catastrophe, thus, more MTs are shorter when present. They also rescue the defect in the KIF21B KOs with 0.5 nM vinblastine, that directly increases catastrophes, shortens the MTs and restores MT network polarization to the synapse. As a functional surrogate they investigate lysosome positioning at the synapse, which is one of the proposed functions of this cytoskeletal polarization. The use of expansion microscopy in this system is relatively new and clearly very powerful. The modelling component adds to the story and supports the sliding model proposed by Poenie and colleagues in 2006, but cannot say that there is no component of end capture and shrinkage as proposed by Hammer and colleagues more recently. Experiments and modelling are performed to a high standard and the results advance the field.

Reviewed by eLife

Competition for MCM Loading at Origins Establishes Replication Timing Patterns

1. Livio Dukaj
2. Nicholas Rhind

Reviewed by Review Commons

Trim39 regulates neuronal apoptosis by acting as a SUMO-targeted E3 ubiquitin-ligase for the transcription factor NFATc3

1. Meenakshi Basu Shrivastava
2. Barbara Mojsa
3. Stéphan Mora
4. Ian Robbins
5. Guillaume Bossis
6. Iréna Lassot
7. Solange Desagher

Reviewed by Review Commons