PLCγ1 is essential for early events in integrin signalling required for cell motility

Abstract

Cell motility is a critical event in many processes and is underlined by complex signalling interactions. Although many components have been implicated in different forms of cell migration, identification of early key mediators of these events has proved difficult. One potential signalling intermediate, PLCγ1, has previously been implicated in growth-factor-mediated chemotaxis but its position and roles in more-complex motility events remain poorly understood. This study links PLCγ1 to early, integrin-regulated changes leading to cell motility. The key role of PLCγ1 was supported by findings that specific depletion of PLCγ1 by small interfering (si)RNA, or by pharmacological inhibition, or the absence of this isoform in PLCγ1–/– cells resulted in the failure to form cell protrusions and undergo cell spreading and elongation in response to integrin engagement. This integrin-PLCγ1 pathway was shown to underlie motility processes involved in morphogenesis of endothelial cells on basement membranes and invasion of cancer cells into such three-dimensional matrices. By combining cellular and biochemical approaches, we have further characterized this signalling pathway. Upstream of PLCγ1 activity, β1 integrin and Src kinase are demonstrated to be essential for phosphorylation of PLCγ1, formation of protein complexes and accumulation of intracellular calcium. Cancer cell invasion and the early morphological changes associated with cell motility were abolished by inhibition of β1 integrin or Src. Our findings establish PLCγ1 as a key player in integrin-mediated cell motility processes and identify other critical components of the signalling pathway involved in establishing a motile phenotype. This suggests a more general role for PLCγ1 in cell motility, functioning as a mediator of both growth factor and integrin-initiated signals.

PLCγ contributes to metastasis of in situ-occurring mammary and prostate tumors

“…EGFR signaling is likely to be the primary trigger as it has been implicated in the transformation, mitogenic and motogenic properties of tumor cells (Carpenter, 2000). However, it is possible that other growth factors or adhesion receptors are signaling via PLCg (Carpenter and Ji, 1999;Jones et al, 2005). As PLCg seems to serve as a point of convergence for PDGF, HGF and IGF-1 in addition to EGF in signaling motility (Bornfeldt et al, 1994;Kundra et al, 1994), expression of PLCz would be expected to diminish cell motility signaled by all of these factors.…”

“…As PLCg seems to serve as a point of convergence for PDGF, HGF and IGF-1 in addition to EGF in signaling motility (Bornfeldt et al, 1994;Kundra et al, 1994), expression of PLCz would be expected to diminish cell motility signaled by all of these factors. Furthermore, PLCg has been linked to integrin-related changes that result in cell motility in the context of invading cancer cells (Jones et al, 2005). The progression of invasive cancers to the morbidity and mortality of metastasis encompasses a series of highly coordinated events, though the literature offers a compelling line of evidence for the motility-related role of PLCg throughout the metastatic process.…”

“…These switches include phospholipase C-g (PLCg), activation of which lies upstream of cytoskeletal reorganization. PLCg appears to be at a convergence point of various signaling pathways leading to spreading and motility, including those from adhesion receptors, and as such offers an opportunity for differential abrogation of multiple yet distinct signaling events (Kassis et al, 1999;Jones et al, 2005). In previous studies, we tested whether PLCg signaling contributes to tumor invasion indirectly through an examination of EGF receptor-mediated invasiveness.…”

Common and Diverging Integrin Signals Downstream of Adhesion and Mechanical Stimuli and Their Interplay with Reactive Oxygen Species

“…ROCK can be activated by integrins via GTP-loaded RhoA (30). MLCK activation requires Ca 2+ -loaded calmodulin and is promoted by (locally) elevated cytoplasmic Ca 2+ levels, which can be induced by integrin-activated phospholipase C (PLC) (40). The activating steps upstream of RhoA GEFs (including p190RhoGEF, p115, GEF-H1, and LARG) (30)) and PLC triggered by integrins are incompletely understood.…”

Glioblastoma: Current Chemotherapeutic Status and Need for New Targets and Approaches

“…Overexpression of epidermal growth factor receptors (EGFR) in glioblastoma multiforme (GBM) promotes PLC 1 activation (Chen et al, 1994;Yang et al, 1994;Wahl et al, 1992). Many functions attributed to PLC 1 activation include proliferation, differentiation, cell motility and invasion of tumor cells (Jones et al, 2005;Wells & Grandis, 2003). Furthermore, PLC 1 is associated with breast cancer metastasis and is highly expressed in breast cancer tissues (Arteaga et al, 1991).…”