Cell News 01/2017
25
Fluorescence fluctuation spectroscopy of protein-protein
interactions in developmental cell-cell fusion
Valentin Dunsing, Benjamin Podbilewicz, Salvatore Chiantia
SESSION 3: NEW INSIGHTS INTO CELL-CELL FUSION:
MECHANISMS OF MEMBRANE FUSION
P
resenting author: Valentin Dunsing
Universität Potsdam, Cell Membrane Biophysics,
Institut für Biologie und Biochemie
Cell-cell fusion is a universal process in development which is
involved in the formation of various organs and tissues. Failure
of fusion leads to severe morphogenic disorders. The epithelial
fusion failure protein EFF-1 was shown to be necessary and
sufficient for fusion in the small nematode C.elegans and cell
culture systems. However, it's mechanism of action remains
poorly understood.
Using fluorescence fluctuation spectroscopy approaches
(Number&Brightness, ScanningFCS) we study the cis and trans
interactions of EFF-1 and its dynamics in the plasma mem-
brane. We find a concentration dependent cis trimerization of
the protein in living cells and monitor cell-cell trans interac-
tions based on cross-correlation.
Finally, we present an experimental setup to investigate EFF-1
interactions in vivo, i.e. epithelial cell-cell fusions in developing
C.elegans embryos.
Cellular dialogs: Cell-cell communication
and fusion in Neurospora crassa
Presenting author: André Fleißner
Technische Universität Braunschweig, Institut für Genetik
In recent years, the red bread mold Neurospora crassa has
advanced as a model organism for studying somatic and sexual
cell fusion. Germinating vegetative spores of this fungus sense
each other and fuse. As a result, a germling network is formed,
which further develops into the mycelial colony. Genetic
analysis combined with live-cell imaging revealed an unusual
mode of communication during these spore interactions. The
two fusion partners appear to coordinately take turns in signal
sending and receiving thereby establishing a kind of “cell-cell
dialog”. This interaction involves the alternating recruitment of
a MAP kinase module and a fungal specific protein to the plas-
ma membrane. Both factors are part of an intricate signaling
network, controlling this unique cellular behavior. Our recent
studies also revealed that the composition of the plasma
membrane is critical for a proper cell-cell interaction. Mutants
accumulating specific ergosterol precursors are deficient in
germling fusion, particularly in the processes after cell-cell
contact, such as contact recognition, cell wall remodeling and
plasma membrane merger. The specific defects correlate with
certain structural features of the different accumulating sterol
precursors, suggesting a strong structure/function relationship.
In summary, our studies identified a fine-tuned signaling
network involving the plasma membrane and a combination
of conserved and fungal-specific signaling factors, which me-
diates the communication and fusion of genetically identical
cells.
