Myosin II motor proteins play important roles in cell migration. Although myosin II filament assembly plays a key role in the stabilization of focal contacts at the leading edge of migrating cells, the mechanisms and signaling pathways regulating the localized assembly of lamellipodial myosin II filaments are poorly understood. We performed a proteomic analysis of myosin heavy chain (MHC) phosphorylation sites in MDA-MB 231 breast cancer cells to identify MHC phosphorylation sites that are activated during integrin engagement and lamellar extension on fibronectin. Fibronectin-activated MHC phosphorylation was identified on novel and previously recognized consensus sites for phosphorylation by protein kinase C and casein kinase II (CK-II). S1943, a CK-II consensus site, was highly phosphorylated in response to matrix engagement, and phosphoantibody staining revealed phosphorylation on myosin II assembled into leading-edge lamellae. Surprisingly, neither pharmacological reduction nor small inhibitory RNA reduction in CK-II activity reduced this stimulated S1943 phosphorylation. Our data demonstrate that S1943 phosphorylation is upregulated during lamellar protrusion, and that CK-II does not appear to be the kinase responsible for this matrix-induced phosphorylation event.
Pubmed ID: 21316371 RIS Download
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A software package and server used to identify and characterize proteins from primary sequence databases using mass spectrometry data. Mascot integrates peptide mass fingerprinting, sequence querying, and MS/MS ion searching in order to search for proteins in databases like SwissProt, NCBInr, EMBL EST divisions, contaminants, and cRAP. If a license is purchased, users may: search data sets that exceed the 1200 spectrum limit of the free version; set up automated, high throughput work; add and edit proteins and quantification methods; and search a preferred collection of sequence databases. The software package works with instruments from AB Sciex, Agilent, Bruker, Jeol, Shimadzu, Thermo Scientific, and Waters.
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