SH4-domain-induced plasma membrane dynamization promotes bleb-associated cell motility

Abstract

SH4 domains provide bipartite membrane-targeting signals for oncogenic Src family kinases. Here we report the induction of non-apoptotic plasma membrane (PM) blebbing as a novel and conserved activity of SH4 domains derived from the prototypic Src kinases Src, Fyn, Yes and Lck as well as the HASPB protein of Leishmania parasites. SH4-domain-induced blebbing is highly dynamic, with bleb formation and collapse displaying distinct kinetics. These reorganizations of the PM are controlled by Rho but not Rac or Cdc42 GTPase signalling pathways. SH4-induced membrane blebbing requires the membrane association of the SH4 domain, is regulated by the activities of Rock kinase and myosin II ATPase, and depends on the integrity of F-actin as well as microtubules. Endogenous Src kinase activity is crucial for PM blebbing in SH4-domain-expressing cells, active Src and Rock kinases are enriched in SH4-domain-induced PM blebs, and PM blebbing correlates with enhanced cell invasion in 3D matrices. These results establish a novel link between SH4 domains, Src activity and Rho signalling, and implicate SH4-domain-mediated PM dynamization as a mechanism that influences invasiveness of cells transformed by SH4-domain-containing oncoproteins.

Differing and isoform-specific roles for the formin DIAPH3 in plasma membrane blebbing and filopodia formation

“…2 h post plating, more than 60% of these HeLa cells displayed prominent PM blebs with some incorporation of F-actin in the bleb rim ( Figure 1A and Supplementary information, Figure S1B). Consistent with reports from other blebbing models [21,25], PM blebbing during HeLa cell adhesion was highly dynamic, characterized by rapid bleb expansion followed by a static phase and subsequent slow retraction of the bleb ( Figure 1A, see also Supplementary information, Movie S1). Moreover, F-actin was only detectable in blebs following the initial expansion phase, but remained associated with the bleb rim during bleb retraction ( Figure 1A, lower panel).…”

“…Blebbing can also be induced experimentally, e.g. by disruption of the genes encoding the actin-membrane crosslinker filamin A or the tumor suppressor p53, or by overexpression of SH4 domain membrane targeting signals [12,[20][21][22][23][24][25]. Despite their distinct physiological context and triggers, PM blebs typically display high dynamics of bleb expansion and retraction.…”

What is the Link Between Protein Aggregation and Interneuronal Lesion Propagation in Neurodegenerative Disease?

“…by activating both the tyrosine kinase and its substrate 179). Such activation can result in fyn-mediated endocytosis via the caveolar pathway (204) or direct release of microvesicles to the extracellular space mediated via the SH4 domain of fyn (or other srk kinases) (34,210). Regulation of endocytosis and exocytosis in neuronal growth cones by srk family kinases regulates endothelial apical endocytosis (77) and has been described in the marine snail Aplysia (223) suggesting that this is an evolutionarily conserved role for fyn-like Srk family kinases in diverse tissues.…”

Dynamics of protein phosphorylation during meiotic maturation

“…The present data reinforce a role for Fyn kinase in what we suggest is an example of cortical maturation. Fyn kinase is associated with changes in cortical actin dynamics of cultured cells [29][30][31] and sertoli cells [32]. Since pTyr proteins localize specifically at the oocyte cortex, we examined the localization of pTyr in oocytes from Fyn (-/-) mice to determine whether Fyn kinase participated in this phosphorylation event.…”