Release of membrane-bound vesicles and inhibition of tumor cell adhesion by the peptide Neopetrosiamide A.
BACKGROUND
Neopetrosiamide A (NeoA) is a 28-amino acid tricyclic peptide originally isolated from a marine sponge as a tumor cell invasion inhibitor whose mechanism of action is unknown.


RESULTS
We show that NeoA reversibly inhibits tumor cell adhesion, disassembles focal adhesions in pre-attached cells, and decreases the level of beta1 integrin subunits on the cell surface. NeoA also induces the formation of dynamic, membrane-bound protrusions on the surface of treated cells and the release of membrane-bound vesicles into the culture medium. Proteomic analysis indicates that the vesicles contain EGF and transferrin receptors as well as a number of proteins involved in adhesion and migration including: beta1 integrin and numerous alpha integrin subunits; actin and actin-binding proteins such as cofilin, moesin and myosin 1C; and membrane modulating eps15 homology domain (EHD) proteins. Surface labeling, trafficking inhibition, and real-time imaging experiments all suggest that beta1 integrin-containing vesicles are released directly from NeoA-induced cell surface protrusions rather than from vesicles generated intracellularly. The biological activity of NeoA is dependent on its disulfide bond pattern and NMR spectroscopy indicates that the peptide is globular with a continuous ridge of hydrophobic groups flanked by charged amino acid residues that could facilitate a simultaneous interaction with lipids and proteins in the membrane.


CONCLUSIONS
NeoA is an anti-adhesive peptide that decreases cell surface integrin levels through a novel, yet to be elucidated, mechanism that involves the release of adhesion molecule-containing vesicles from the cell surface.
Austin
Pamela
P
Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
Heller
Markus
M
Williams
David E
DE
McIntosh
Lawrence P
LP
Vogl
A Wayne
AW
Foster
Leonard J
LJ
Andersen
Raymond J
RJ
Roberge
Michel
M
Roskelley
Calvin D
CD
D002448:Cell Adhesion / Q000187:drug effects; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism*; D022081:Cell Surface Extensions / Q000187:drug effects / Q000648:ultrastructure; D022162:Cytoplasmic Vesicles / Q000187:drug effects* / Q000378:metabolism*; D022001:Focal Adhesions / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D009361:Neoplasm Invasiveness; D009369:Neoplasms / Q000378:metabolism* / Q000473:pathology*; D010456:Peptides, Cyclic / Q000737:chemistry / Q000494:pharmacology*; D021122:Protein Subunits / Q000378:metabolism; D013696:Temperature
D019012:Integrin beta1; D008565:Membrane Proteins; D010456:Peptides, Cyclic; D021122:Protein Subunits; C512184:neopetrosiamide A