Memo is a cofilin-interacting protein that influences PLCgamma1 and cofilin activities, and is essential for maintaining directionality during ErbB2-induced tumor-cell migration.
Heregulin (HRG) activates ErbB2-ErbB3 heterodimers thereby stimulating many cellular responses, including motility. Memo and PLCgamma1 interact with ErbB2 autophosphorylation sites and are essential for HRG-induced chemotaxis. By tracing HRG-stimulated cell migration in Dunn chambers, we found that Memo- or PLCgamma1 knockdown (KD) strongly impairs cell directionality. Memo has no obvious enzymatic activity and was discovered via its ability to complex with ErbB2. Using the yeast two-hybrid approach to gain insight into Memo function, an interaction between Memo and cofilin, a regulator of actin dynamics, was uncovered. The interaction was confirmed in vitro using recombinant proteins and in vivo in co-immunoprecipitation experiments where Memo was detected in complexes with cofilin, ErbB2 and PLCgamma1. Interestingly, in Memo KD cells, HRG-induced PLCgamma1 phosphorylation was decreased, suggesting that Memo regulates PLCgamma1 activation. Furthermore, HRG-induced recruitment of GFP-cofilin to lamellipodia is impaired in Memo and in PLCgamma1 KD cells, suggesting that both proteins lie upstream of cofilin in models of ErbB2-driven tumor-cell migration. Finally, in vitro F-actin binding and depolymerization assays showed that Memo enhances cofilin depolymerizing and severing activity. In summary, these data indicate that Memo also regulates actin dynamics by interacting with cofilin and enhancing its function.
Meira
Maria
M
Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland.
Masson
Régis
R
Stagljar
Igor
I
Lienhard
Susanne
S
Maurer
Francisca
F
Boulay
Anne
A
Hynes
Nancy E
NE
D051339:Actin Depolymerizing Factors / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D001681:Biological Assay; D001943:Breast Neoplasms / Q000201:enzymology / Q000473:pathology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D002633:Chemotaxis / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D009369:Neoplasms / Q000201:enzymology* / Q000473:pathology*; D020890:Neuregulin-1 / Q000494:pharmacology; D019159:Nonheme Iron Proteins / Q000378:metabolism*; D051966:Phospholipase C gamma / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D011554:Pseudopodia / Q000187:drug effects / Q000201:enzymology; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism
D051339:Actin Depolymerizing Factors; D000199:Actins; D049452:Green Fluorescent Proteins; D047908:Intracellular Signaling Peptides and Proteins; D020890:Neuregulin-1; D019159:Nonheme Iron Proteins; D051966:Phospholipase C gamma; D018719:Erb-b2 Receptor Tyrosine Kinases; D011993:Recombinant Fusion Proteins; C527585:MEMO1 protein, human; C508053:ERBB2 protein, human