Cell and Developmental biology

vivek
Intracellular Compartmentation

Group Structure

GROUP LEADER:
Vivek Malhotra (ICREA Research Professor and coordinator of the Cell and Developmental Biology Programme)
STAFF SCIENTIST:
Sandra Mitrovic
POSTDOCTORAL FELLOWS:
Antonios Santos (since October), Cristina Nogueira, Patrik Erlmann, David Cruz García, Josse Van Galen, Julien Villeneuve (until October), Juan Duran Serrano, Felix Campelo Aubarell, Amy Curwin, Gerard Cantero (since September)
PhD STUDENT:
Caroline Bruns (until April)
TECHNICIAN:
Maria Ortega, Jean-François Popoff, Margherita Scarpa

Summary

We continue to unravel the mechanism of cell compartmentation and protein secretion. The specific aims follow.

Our work has led to the identification of a serine threonine kinase called PKD that controls membrane fission to generate transport carriers that are destined to the cell surface. The targets of PKD are mostly proteins that affect lipid composition and sense, or induce, membrane curvature. Our current studies are aimed at reconstituting PKD mediated membrane fission in vitro.

PKD was identified as a protein required for the Ilimaquinone (IQ) mediated vesiculation of the stacked Golgi cisternae. Our new findings reveal the activation of a specific phospholipase by IQ at the Golgi. Chromatography of isolated and detergent solubilized Golgi membranes is in progress to identify this activity for its characterization in membrane fission event.

Genome wide screening approaches has uncovered the involvement of novel proteins in secretion of specific cargoes such as the collagens and mucins. These components, in addition to chemical screens to search for inhibitors that affect mucin secretion are the subject of our on-going efforts.

We identified a new compartment called CUPS and a number of genes required for the secretion of signal sequence lacking proteins secreted by human cells. The mechanism of this unconventional secretion by which proteins such as interleukin (IL)-1, 18 and 37, MIF, tissue transglutaminase, Acyl-CoA binding protein et cetera are secreted, and the dynamics of CUPS is a major focus of the lab.

We identified a calcium dependent process for the sorting of secretory cargo at the TGN. Some of these cargoes are transported in a new class of transport carriers called CARTS. We are reconstituting the sorting and packing of secretory cargoes in CARTS in vitro.

Highlights

We have performed a genome wide screen and identified 16 novel proteins that regulate mucin secretion by human colon cancer cells (Mitrovic et al., 2013). Our aim is to understand the function of these proteins and use our findings to search for chemicals that could be used to control mucin release by the human cells

We have identified the involvement of a Bar domain containing protein in PKD dependent generation of secretory granules at the Trans Golgi network ( Cruz-Garcia et al., 2013)

Our new findings reveal the ER-Golgi membrane associated protein Myt1 as downstream target of MEK1 in the events regulating Golgi membrane organization and entry of cell into mitosis (Vileneuve et al., 2013).


Research Projects

  • Mechanism of mucin secretion.
  • Mechanism of collagen export from the ER.
  • Mechanism of transport carrier formation at the Trans Golgi network.
  • Mechanism of unconventional protein secretion.

Different export routes for secretory cargo at the ER. Figure 1. Different export routes for secretory cargo at the ER.


Selected Publications

  1. Villeneuve J, Scarpa M, Ortega Bellido M, and Malhotra V.
    “MEK1 inactivates Myt1 to regulate Golgi membrane fragmentation and mitotic entry in mammalian cells.”
    EMBO J, 32:72-85 (2013).
  2. Mitrovic S, Nogueira C, Cantero-Recasens G, Kiefer K, Fernández-Fernández JM, Popoff JF, Casano L, Bard FA, Gomez R, Valverde MA, Malhotra V.
    “TRPM5-mediated calcium uptake regulates mucin secretion from human colon goblet cells.”
    Elife, 2:e00658 (2013).
  3. Malhotra V.
    “Unconventional protein secretion: an evolving mechanism.”
    EMBO J, 32:1660-1664 (2013).
  4. Cruz-Garcia D, Ortega-Bellido M, Scarpa M, Villeneuve J, Jovic M, Porzner M, Balla T, Seufferlein T, and Malhotra V.
    “PI(4)P-dependent recruitment of arfaptins to the trans-Golgi network and their involvement in cargo export.”
    EMBO J, 32:1717-1729 (2013).
  5. Wakana Y, Villeneuve J, van Galen J, Cruz-Garcia D, Tagaya M, and Malhotra V.
    “Kinesin-5/Eg5 is important for transport of CARTS from the trans-Golgi network to the cell surface.”
    J Cell Biol, 202:241-250 (2013).