Profilin induces lamellipodia by growth factor-independent mechanism.
Profilin has been implicated in cell motility and in a variety of cellular processes, such as membrane extension, endocytosis, and formation of focal complexes. In vivo, profilin replenish the pool of ATP-actin monomers by increasing the rate of nucleotide exchange of ADP-actin for ATP-actin, promoting the incorporation of new actin monomers at the barbed end of actin filaments. For this report, we generated a membrane-permeable version of profilin I (PTD4-PfnI) for the alteration of intracellular profilin levels taking advantage of the protein transduction technique. We show that profilin I induces lamellipodia formation independently of growth factor presence in primary bovine trabecular meshwork (BTM) cells. The effects are time- and concentration-dependent and specific to the profilin I isoform. Profilin II, the neuronal isoform, failed to extend lamellipodia in the same degree as profilin I. H133S, a mutation in the polyproline binding domain, showed a reduced ability to induce lamellipodia. H199E, mutation in the actin binding domain failed to induce membrane spreading and inhibit fetal bovine serum (FBS) -induced lamellipodia extension. Incubation with a synthetic polyproline domain peptide (GP5)3, fused to a transduction domain, abolished lamellipodia induction by profilin or FBS. Time-lapse microscopy confirmed the effects of profilin on lamellipodia extension with a higher spreading velocity than FBS. PTD4-Pfn I was found in the inner lamellipodia domain, at the membrane leading edge where it colocalizes with endogenous profilin. While FBS-induced lamellipodia formation activates Rac1, PTD4-Pfn I stimulation did not induce Rac1 activation. We propose a role of profilin I favoring lamellipodia formation by a mechanism downstream of growth factor.
Syriani
Enrique
E
IDIBAPS-Department of Physiological Sciences I, Facultad de Medicina-University of Barcelona, Barcelona, Spain.
Gomez-Cabrero
Azucena
A
Bosch
Marta
M
Moya
Alicia
A
Abad
Elena
E
Gual
Arcadi
A
Gasull
Xavier
X
Morales
Miguel
M
D000199:Actins / Q000378:metabolism; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D047630:Depsipeptides / Q000494:pharmacology; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology; D009281:Naphthalenes / Q000494:pharmacology; D010455:Peptides / Q000378:metabolism; D010590:Phalloidine / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051304:Profilins / Q000378:metabolism / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011554:Pseudopodia / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000494:pharmacology*; D014129:Trabecular Meshwork / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
D000199:Actins; D001381:Azepines; D047630:Depsipeptides; D036341:Intercellular Signaling Peptides and Proteins; D009281:Naphthalenes; D010455:Peptides; D051304:Profilins; D011993:Recombinant Fusion Proteins; C057531:jasplakinolide; C070571:ML 7; D010590:Phalloidine; C011083:polyproline; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D020830:rac1 GTP-Binding Protein