Tag Archives: endocytosis

Journal Club on Monday, August 6

For Journal Club on August 6, Eric Lewellyn presented the following paper:

Actin filament severing by cofilin dismantles actin patches and produces mother filaments for new patches. Chen Q, Pollard TD. Curr Biol. 2013 Jul 8;23(13):1154-62. PMID: 23727096.

Chen & Pollard Curr Biol 2013

“Sever, diffuse and trigger” model for actin filament turnover in actin patches. The 7 steps (numbers next to the arrows) are (1) clathrin coated pits bind adaptor proteins End4p and Pan1p, (2) short, diffusing actin filaments bind to End4p and Pan1p associated with coated pits, and (3) Arp2/3 complex interacts with these mother filaments and nucleation promoting factors to (4) initiate branching nucleation of actin filaments that promote elongation of the endocytic tubule. (5) After abscission of the vesicle, (6) cofilin severs actin filaments to generate a pool of short, diffusing actin filaments, some of which return to the cycle at step 2.

Journal Club on Monday, June 3

For our Journal Club on June 3, Daphné Dambournet presented the following paper:

Divergent modes for cargo-mediated control of clathrin-coated pit dynamics. Soohoo AL, Puthenveedu MA. Mol Biol Cell. 2013 Jun;24(11):1725-34. PMID: 23536704.

Soohoo MBoC 2013

Model for divergent modes of cargo-mediated control of endocytosis by signaling receptors.

Journal Club on Monday, April 29

For our Journal Club on April 29, Sun Hae Hong presented the following paper:

The molecular basis for the endocytosis of small R-SNAREs by the clathrin adaptor CALM. Miller SE, Sahlender DA, Graham SC, Höning S, Robinson MS, Peden AA, Owen DJ. Cell. 2011 Nov 23;147(5):1118-31. PMID: 22118466

Schematic representation of the model of VAMP8 trafficking from the plasma membrane.

Journal Club on Monday, March 17

For our Journal Club on March 17, Rebecca Lu will present the following paper:

Robust polarity establishment occurs via an endocytosis-based cortical corralling mechanism. Jose M, Tollis S, Nair D, Sibarita JB, McCusker D. J Cell Biol. 2013 Feb 18;200(4):407-18. PMID: 23401000

Schematics illustrating the mathematical model. Shown are the Cdc42 autoamplification module (A), the complete endocytosis module (B), the exocytosis module (C), and a legend for graphics (D).

The Drubin/Barnes Lab Has a New Theme Song!

We now present to you a brand new theme song to introduce the world to all of the awesome people in the Drubin/Barnes Lab!

The Drubin-Barnes Lab!
(Parody of The Brady Bunch Theme Song)

Submission for UC-Berkeley MCB Follies 2012-2013
(UC-Berkeley, Dept. of Molecular and Cell Biology)

LYRICS, VOCALS, CAMERA, EDITING:  Nathaniel Krefman

ADDITIONAL VOCALS:  Akemi Kunibe

STARRING:  The Drubin/Barnes Lab at UC-Berkeley (Fall 2012)!

PIs:  Profs. David Drubin and Georjana Barnes

1st GROUP (microtubules, spindles, kinetochores, & mitosis in budding yeast):  Adrianne Pigula (top left), Nathaniel Krefman (center left), Itziar Ibarlucea-Benitez (bottom left), Prof. Georjana Barnes (center), Anthony Cormier (center right)

2nd GROUP (actin cytoskeleton and endocytosis in mammalian cells and budding yeast):  Aaron Cheng (top left square, left), Jasper Weinberg (top left square, right), Rebecca Lu (center left square, left), Lillie Cohn (center left square, center), Akemi Kunibe (center left square, right), Yansong Miao (bottom left square), Prof. David Drubin (center square), Sun Hae Hong (top right square, left), Yidi Sun (top right square, right), Alex Grassart (center right square, left), Daphne Dambournet (center right square, right), Christa Cortesio (bottom right square, left), Eric Lewellyn (bottom right square, right).

________________________________________________

LYRICS:

Here’s the story of a lovely lady.
Who studied what a microtubule’s for.
All her group loves mitosis, like Georjana,
And kinetochores.

Here’s the story of a PI named David,
Who was interested in actin in live cells,
And his group mapped endocytosis dynamics,
Yet they were by themselves.

After their post-docs, where the lady met this fellow,
And named a protein complex DAM instead of DARN,
They knew their groups must form one laboratory.
That’s the way our lab became the Drubin/Barnes!
The Drubin/Barnes!

That’s the way our lab became the Drubin/Barnes!

Journal Club on Monday, January 7

For our Journal Club on January 7, Yidi Sun presented the following paper:

PtdIns4P synthesis by PI4KIIIα at the plasma membrane and its impact on plasma membrane identity.  Nakatsu F, Baskin JM, Chung J, Tanner LB, Shui G, Lee SY, Pirruccello M, Hao M, Ingolia NT, Wenk MR, De Camilli P.  J Cell Biol. 2012 Dec 10;199(6):1003-16.  PMID:  23229899.

Congratulations to Yidi Sun on her new paper!

Yidi Sun‘s new paper is out now as an electronic publication ahead of print in the Journal of Cell Science.  Congratulations to Yidi on her great work!  The abstract is below.  The PDF can be downloaded from JCS here.

The functions of anionic phospholipids during clathrin-mediated endocytosis site initiation and vesicle formation. Sun Y, Drubin DG. J Cell Sci. 2012 Oct 24. PMID: 23097040.

Abstract

Anionic phospholipids PI(4,5)P(2) and phosphatidylserine (PS) are enriched in the cytosolic leaflet of the plasma membrane where endocytic sites form. In this study, we investigated the roles of PI(4,5)P(2) and PS in clathrin-mediated endocytosis (CME) site initiation and vesicle formation in Saccharomyces cerevisiae. Live-cell imaging of endocytic protein dynamics in an mss4(ts) mutant, which has severely reduced PI(4,5)P(2) levels, revealed that PI(4,5)P(2) is required for endocytic membrane invagination but is less important for endocytic site initiation. We also demonstrated that in various deletion mutants of genes encoding components of the Rcy1-Ypt31/32 GTPase pathway, endocytic proteins dynamically assemble not only on the plasma membrane but also on intracellular membrane compartments, which are likely derived from early endosomes. In rcy1Δ cells, fluorescent biosensors indicated that PI(4,5)P(2) only localized to the plasma membrane while PS localized to both the plasma membrane and intracellular membranes. Furthermore, we found that polarized endocytic patch establishment is defective in the PS-deficient cho1Δ mutant. We propose that PS is important for directing endocytic proteins to the plasma membrane and that PI(4,5)P(2) is required to facilitate endocytic membrane invagination.

Lighting Up Live Cells with Fluorescence (Genetic Engineering & Biotechnology News)

Genetic Engineering & Biotechnology News is out with a Feature Article this week including some comments from David Drubin about targeted genome modification in mammalian cells for fluorescence microscopy studies.

Lighting Up Live Cells with Fluorescence. Christine Herman. GEN. Sep 1, 2012 (Vol. 15, No. 32)

“The difference between taking snapshots of the process and watching a movie is just night and day,” says David Drubin, Ph.D., professor of cell and developmental biology at the University of California, Berkeley, whose lab uses fluorescence to understand the intricate details underlying clathrin-mediated endocytosis.

 

Researchers in David Drubin’s lab at the University of California, Berkeley genetically engineered a human cell line to express endogenous levels of RFP-tagged clathrin light chain A (red) and GFP-tagged dynamin 2 (green) for studying clathrin-mediated endocytosis. The above 3D kymograph of the cell surface, with the time dimension in the z-axis, shows the full lifetime of hundreds of clathrin patches on the membrane, which terminate upon recruitment of dynamin. [Aaron T. Cheng]

An Interview with David Drubin in Biowire

The May 2012 edition of Biowire, a publication of Sigma-Aldrich, includes an interview with David Drubin about the projects in our lab looking at clathrin-mediated endocytosis (CME) in mammalian cells using zing finger nuclease (ZFN) technology to undertake targeted genome modification. Traditionally, CME has been studied in cells in which fluorescently-tagged components of endocytic machinery are overexpressed using exogenous constructs. Data obtained in many labs using these methods suggested that CME was highly variable. Using ZFN technology, in collaboration with Sangamo Biosciences, our lab recently showed that CME is robust and efficient in mammalian cells.  The new results highlight the technical advantages of tagging genes at their endogenous loci, an approach that has been historically limited to genetically tractable organisms, such as the Drubin/Barnes Lab favorite Saccharomyces cerevisiae (budding yeast).  Emerging technologies, such as ZFNs and TALENs, however, are now making this sort of precise genomic manipulation possible in animal cells, including human cells, giving us new and powerful ways of studying cellular biology.

Cellular processes should be studied as close to their natural states as possible. I suspect that, as we see more uses of zinc finger nucleases [for tagging endogenous genes], people will find that they have been inadvertently perturbing the processes that they have been studying.

David Drubin (Biowire, May 2012)