mTORC2 Regulates Neutrophil Chemotaxis in a cAMP- and RhoA-Dependent Fashion

Abstract

SUMMARY We studied the role of the target of rapamycin complex 2 (mTORC2) during neutrophil chemotaxis, a process that is mediated through the polarization of actin and myosin filament networks. We show that inhibition of mTORC2 activity, achieved via knock down (KD) of Rictor, severely inhibits neutrophil polarization and directed migration induced by chemoattractants, independently of Akt. Rictor KD also abolishes the ability of chemoattractants to induce cAMP production, a process mediated through the activation of the adenylyl cyclase 9 (AC9). Cells with either reduced or higher AC9 levels also exhibit specific and severe tail retraction defects that are mediated through RhoA. We further show that cAMP is excluded from extending pseudopods and remains restricted to the cell body of migrating neutrophils. We propose that the mTORC2-dependent regulation of MyoII occurs through a cAMP/RhoA signaling axis, independently of actin reorganization during neutrophil chemotaxis.

Front Signal-Dependent Accumulation of RHOA Inhibitor FAM65B at Leading Edges Polarizes Neutrophils

“…On the one hand, the mechanism underlies the rapid polarization of RHOA activity that is uniformly activated by Lfc. This FAM65-mediated mechanism might be part of or interact with the aforementioned mechanisms mediated by mTORC2-PKC (Liu et al, 2010), PI3K (Van Keymeulen et al, 2006;Yoo et al, 2010), PDZRhoGEF (Wong et al, 2007) and possibly others, in sharpening and stabilizing the polarity. On the other hand, the mechanism reduces the adhesion (Fig.…”

“…In addition, studies in HL-60 differentiated neutrophil-like cells and zebrafish neutrophils have revealed RAC-independent, but phosphoinositide 3-kinase (PI3K)-dependent, mechanisms for the regulation of RHOA and pMLC (Van Keymeulen et al, 2006;Yoo et al, 2010). Moreover, an mammalian target of rapamycin complex 2 (mTORC2) to adenylate cyclase 9 (AC9, also known as ADCY9) pathway has been shown to exclude cAMP from the front and regulate RHOA and pMLC, probably in a protein kinase C (PKC)-dependent mechanism (Liu et al, 2010). Disruption of this pathway results in increased pMLC at the front of the cell.…”

Hypoxia and Pulmonary Hypertension

“…mTORC1 is composed of mTOR, Raptor, LST8/GβL, PRAS40 and DEP domain containing mTOR-interacting protein (DEPTOR), and its activity is stimulated by growth factor signals to regulate protein synthesis through 4E-BP1/BP2 and the S6 kinases, S6K1 and S6K2 [74,75]. By contrast, mTORC2, which comprises mTOR, Rictor, LST8/GβL, DEPTOR, SIN1 and PRR5, regulates cytoskeletal organisation [76,77] and has a role in phosphorylation of protein kinase C (PKC), protein kinase B (PKB) and serum-and glucocorticoid-induced protein kinase (SGK) to promote cell survival and cell cycle progression [78][79][80].…”

WD40-repeat proteins control the flow of Gβγ signaling for directional cell migration

“…[15][16][17][18][19][20] It remains to be seen if WDR26 and RACK1 influence Gβγ-mediated activation of these effectors, and whether this regulation contributes to directional migration in leukocytes.…”

“…6 In addition to the PI3K pathway, several other pathways, including those mediated by PLCβ 2/3 , PLA 2 , p38 MAPK, pREX1 and mTORC2 have now been shown to act in parallel or in concert with the PI3K pathway to regulate leukocyte migration. [15][16][17][18][19][20] These pathways are all activated downstream of Gβγ. However, beside PI3Kγ, PLCβ2/3 and pREX1, which are directly activated by Gβγ, the biochemical nature of the other pathways involved in leukocyte chemotaxis remains poorly defined because the direct binding targets of Gβγ have not been identified.…”