L‐plastin Ser5 phosphorylation in breast cancer cells andin vitrois mediated by RSK downstream of the ERK/MAPK pathway

Abstract

Deregulated cell migration and invasion are hallmarks of metastatic cancer cells. Phosphorylation on residue Ser5 of the actin-bundling protein L-plastin activates L-plastin and has been reported to be crucial for invasion and metastasis. Here, we investigate signal transduction leading to L-plastin Ser5 phosphorylation using 4 human breast cancer cell lines. Whole-genome microarray analysis comparing cell lines with different invasive capacities and corresponding variations in L-plastin Ser5 phosphorylation level revealed that genes of the ERK/ MAPK pathway are differentially expressed. It is noteworthy that in vitro kinase assays showed that ERK/MAPK pathway downstream ribosomal protein S6 kinases a-1 (RSK1) and a-3 (RSK2) are able to directly phosphorylate L-plastin on Ser5. Small interfering RNA-or short hairpin RNA-mediated knockdown and activation/inhibition studies followed by immunoblot analysis and computational modeling confirmed that ribosomal S6 kinase (RSK) is an essential activator of L-plastin. Migration and invasion assays showed that RSK knockdown led to a decrease of up to 30% of migration and invasion of MDA-MB-435S cells. Although the presence of L-plastin was not necessary for migration/invasion of these cells, immunofluorescence assays illustrated RSK-dependent recruitment of Ser5-phosphorylated L-plastin to migratory structures. Altogether, we provide evidence that the ERK/MAPK pathway is involved in L-plastin Ser5 phosphorylation in breast cancer cells with RSK1 and RSK2 kinases able to directly phosphorylate L-plastin residue Ser5.-Lommel, M. J., Trairatphisan, P., Gäbler, K., Laurini, C., Muller, A., Kaoma, T., Vallar, L., Sauter, T., Schaffner-Reckinger, E. L-plastin Ser5 phosphorylation in breast cancer cells and in vitro is mediated by RSK downstream of the ERK/MAPK pathway. FASEB J. 30, 1218FASEB J. 30, -1233FASEB J. 30, (2016. www.fasebj.org

Angiotensin II regulates phosphorylation of actin‐associated proteins in human podocytes

“…Similar to that in breast cancer cells (39), LCP1 phosphorylation in podocytes was influenced by ERK, RSK, PKA, and PKC activity (Fig. 3), which suggests that LCP1 phosphorylation by these kinases is not limited to certain cell types and is also present in podocytes.…”

“…LPS is known as a podocyte-affecting substance, which leads in vivo to foot process effacement and damage to the slit diaphragm (38). To examine whether podocyte damage in general leads to LCP1 It has been demonstrated in breast cancer cell lines that ERK, RSK, PKA, and PKC are involved in the regulation of LCP1 phosphorylation at Ser5 (27,39,40); therefore, we investigated whether these kinases are also responsible for LCP1 phosphorylation in podocytes. Treatment with the specific RSK inhibitor, BID1870 (41), or the ERK inhibitor, U0126 (42), completely blocked AngII-induced LCP1 phosphorylation, which demonstrated that ERK and RSK are involved in LCP1 phosphorylation also in podocytes.…”

LRRK1 regulation of actin assembly in osteoclasts involves serine 5 phosphorylation of L‐plastin

“…Lommel et. al recently provided evidence that the ERK/MAPK pathway was involved in L-plastin serine 5 phosphorylation in breast cancers, with ribosomal S6 kinase 1 and 2 able to directly phosphorylate the L-plastin serine 5 residue (19) . Other potential candidate kinases that are involved in L-plastin phosphorylation are PKC and PI3K (20-22) .…”

“…[16][17][18] Although in vivo and in vitro phosphorylation of serine 5 by cyclic adenosine monophosphate (cAMP)dependent protein kinase A is well documented, it is still unknown which kinase(s) phosphorylate serine 7. 17,18 Lommel et al 19 recently provided evidence that the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) pathway was involved in L-plastin serine 5 phosphorylation in breast cancers, with ribosomal S6 kinase 1 and 2 able to directly phosphorylate the L-plastin Other potential candidate kinases that are involved in L-plastin phosphorylation are PKC and PI3K. [20][21][22] Interestingly, the N-terminal sequence of L-plastin proteins (RGSVS) does bear the consensus substrate motifs (R/KxS) for PKC protein kinases.…”

Boolean network modeling in systems pharmacology

“…The application of PBNs for describing and analyzing complex biological systems has been reviewed [60]. PBN modeling has been used as a mathematical framework to describe cancer-specific intracellular signaling of deregulated platelet-derived growth factor in gastrointestinal stromal tumors and the differential regulation of L-plastin phosphorylation by genes of the ERK/MAPK pathway across four breast cancer cell lines [31,61]. …”