Cell-cell fusion is fundamental to the development and physiology of multicellular organisms, but little is known of its mechanistic underpinnings. Recent studies in several model systems have begun to reveal fundamental principles underlying cell-cell fusion. In particular, studies in the fruit fly Drosophila have revealed an essential function of the actin cytoskeleton in myoblast fusion, the process in which mononucleate myoblasts fuse to form multinucleate muscle fibers. Specifically, we have revealed a cell type-specific, F-actin-enriched podosome-like structure that invades the opposing fusion partner with multiple protrusive fingers, which ultimately leads to fusion pore formation. In addition, studies in the round worm C. elegans have identified a pair of putative fusogenic proteins that are both necessary and sufficient to induce fusion in the embyro. Moreover, it has been shown that expressing the worm fusogens in a heterologous insect cell line, Sf9 cells can induce a low frequency of cell-cell fusion. We have now established a high-efficiency, inducible cell culture system by co-expressing the worm fusogen and a fly cell adhesion molecule in a Drosophila cell line that does not normally undergo fusion. Such co-expression results in a >10 fold increase in cell fusion efficiency compared with cells expressing the fusogen alone. We show that similar podosome-like structures are used in cultured cells to promote cell-cell fusion and that the Arp2/3 nucleation promoting factors are required for fusing cultured cells as for muscle cells in Drosophila embryos. Thus we have established a cell culture system that closely mimics myoblast fusion in vivo. The goal of this project is to further characterize the molecular and cellular mechanisms of this cell culture system and to use it as a tool to discover new genes involved in cell-cell fusion.

Public Health Relevance

Cell-cell fusion is fundamental to the conception, development and physiology of multicellular organisms. It is involved in processes as diverse as fertilization, myogenesis, bone remodeling, placental development, immune response and tumor metastasis. Thus understanding the mechanisms of cell-cell fusion is not only important for fundamental biology, but may also provide basis for its manipulation in therapeutic settings for human diseases.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM098816-01A1
Application #
8294190
Study Section
Intercellular Interactions (ICI)
Program Officer
Chin, Jean
Project Start
2012-04-01
Project End
2016-03-31
Budget Start
2012-04-01
Budget End
2013-03-31
Support Year
1
Fiscal Year
2012
Total Cost
$307,800
Indirect Cost
$117,800
Name
Johns Hopkins University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
001910777
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Shilagardi, Khurts; Li, Shuo; Luo, Fengbao et al. (2013) Actin-propelled invasive membrane protrusions promote fusogenic protein engagement during cell-cell fusion. Science 340:359-63