Diacylglycerol kinase α mediates HGF-induced Rac activation and membrane ruffling by regulating atypical PKC and RhoGDI

Abstract

Diacylglycerol kinases (DGKs) convert diacylglycerol (DAG) into phosphatidic acid (PA), acting as molecular switches between DAG-and PA-mediated signaling. We previously showed that Srcdependent activation and plasma membrane recruitment of DGKα are required for growth-factor-induced cell migration and ruffling, through the control of Rac small-GTPase activation and plasma membrane localization. Herein we unveil a signaling pathway through which DGKα coordinates the localization of Rac. We show that upon hepatocyte growth-factor stimulation, DGKα, by producing PA, provides a key signal to recruit atypical PKCζ/ι (aPKCζ/ι) in complex with RhoGDI and Rac at ruffling sites of colony-growing epithelial cells. Then, DGKα-dependent activation of aPKCζ/ι mediates the release of Rac from the inhibitory complex with RhoGDI, allowing its activation and leading to formation of membrane ruffles, which constitute essential requirements for cell migration. These findings highlight DGKα as the central element of a lipid signaling pathway linking tyrosine kinase growth-factor receptors to regulation of aPKCs and RhoGDI, and providing a positional signal regulating Rac association to the plasma membrane.cell migration | growth factors | phosphatidic acid C ell migration, central to many biological and pathological processes such as cancer metastatic progression, is a multistep cycle involving extension of protrusions and formation of stable attachments near the leading edge, followed by translocation of the cell body forward (1). The protrusive activity occurring at the leading edge depends on the spatial and temporal coordination between cell substrate adhesion and actin reorganization. Rhofamily small GTPases coordinate the recruitment at the leading edge of downstream effectors, thereby mediating the formation of ruffles and lamellipodia. Their GTP-bound state is tightly regulated by both guanine nucleotide exchange factors (GEFs), which stimulate GTP loading, and GTPase activating proteins (GAPs), which catalyze GTP hydrolysis. Moreover, Rho-family GTPases are regulated by guanine nucleotide dissociation inhibitors (GDIs), which antagonize both GEFs and GAPs and mediate the cycling of Rho proteins between the cytosol and the membrane (2, 3).Atypical protein kinase C ζ and ι (aPKCζ/ι), unlike classical and novel PKCs, feature a C1-like domain which does not bind to either diacylglycerol or phorbol esters, and have recently been proposed as key transducers for establishment of cell polarity and migration (4).Diacylglycerol kinases (DGKs), which convert diacylglycerol (DAG) to phosphatidic acid (PA), comprise a family of 10 distinct enzymes grouped into five classes, each featuring distinct regulatory domains and a highly conserved catalytic domain preceded by two cysteine-rich C1-like domains. An increasing body of evidence indicates that DGKs, by acting as terminators of diacylglyceroltriggered signaling, contribute to regulating C1 domain-containing proteins, such as classical and novel PKCs and the Rac-GAP β-chimaerin (5). ...

Oncogenic Activity of Ect2 Is Regulated through Protein Kinase Cι-mediated Phosphorylation

“…6C). Furthermore, the level of Thr(P)-328-Ect2 is greatly increased in the presence of phosphatidic acid, a known activator of atypical PKCs (23)(24)(25). These data demonstrate that PKC directly phosphorylates Ect2 at Thr-328 in vitro.…”

Redundant and specialized roles for diacylglycerol kinases α and ζ in the control of T cell functions

“…DGKz-mediated generation of PA promotes neurite outgrowth by activating p21-activated kinase 1 (PAK1), which phosphorylates Rho-family guanine nucleotide dissociation inhibitors (RhoGDIs) and causes the dissociation of this inhibitor from Rac1 (43,61). A similar mechanism is proposed for DGKa in epithelial cells, in which the PA-dependent recruitment of the atypical PKCz mediates the release of Rac from the inhibitory RhoGDI complex (62). At the immunological synapse, PKCz promotes polarization of the microtubule-organizing center (MTOC) in both CD4 + and CD8 + T cells (63).…”

Nuclear Envelope Phosphatase 1-Regulatory Subunit 1 (Formerly TMEM188) Is the Metazoan Spo7p Ortholog and Functions in the Lipin Activation Pathway

“…For example, PA activates mammalian target of rapamycin, S6 kinase, and other mitogenic signaling molecules, recruits PKCs and RhoGDIs to membranes for cytoskeletal rearrangements and cell migration, and is involved in vesicle budding and fusion (1)(2)(3)(4)(5). DAG activates several signaling molecules such as PKCs, PKDs, and ion channels through their C-1 domains (6 -8).…”