Dataset Information

Identification of Syntaxin 7 and 12 as the first selective substrates for SGK3

ABSTRACT: Deregulation of the PI3K/Akt pathway is a common feature in many types of cancer. Recent data has demonstrated that prolonged inhibition of breast cancer cell lines with PI3K and Akt inhibitors leads to up-regulation and increased activity of the AGC kinase Serum and glucocorticoid activated kinase 3, SGK3, which in turn substitutes for Akt and leads to activation of mTORC1. SGK3 and Akt exhibit similar substrate specificity for Ser/Thr residues in the RxRxxS/T motif. However, SGK3 can be regulated by both PI3K class I and class III and possesses a unique PX domain, enabling it to bind to PI(3)P lipids in endosomes. Still, the known SGK3 substrates are either shared or have not been tested whether Akt can phosphorylate them. In the present study, we undertook genetic and pharmacologic phosphoproteomic screens to search for selective SGK3 substrates. We identified a significant number of potential in vivo SGK3 selective substrates, including the endosomal proteins STX7, STX12, RFIP4 and WDR44. In vitro phosphorylation studies demonstrated that these substrates were directly phosphorylated at the sites identified in vivo by SGK3 but, unlike all other SGK3 substrates reported, not by Akt. We provide evidence that endogenous STX7 and STX12 are physiological SGK3 substrates whose phosphorylation is potently stimulated by IGF1. Our data pinpoint that STX7 and STX12 are the first selective SGK3 substrates in vivo and this phosphorylation enhances their interaction with the respective SNARE complexes. Finally, we suggest that STX7 and STX12 phosphorylation can be utilised as in vivo biomarkers for SGK3 activity.

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Raja Sekhar Nirujogi

LAB HEAD: Prof Matthias Trost

PROVIDER: PXD014561 | Pride | 2020-05-26

REPOSITORIES: Pride

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Dataset's files

Source:

			Action	DRS
	20160530_DRM_ppBrp_fr1.raw	Raw
	20160530_DRM_ppBrp_fr10.raw	Raw
	20160530_DRM_ppBrp_fr10_160605065130.raw	Raw
	20160530_DRM_ppBrp_fr11.raw	Raw
	20160530_DRM_ppBrp_fr11_160605110526.raw	Raw

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Publications

Phosphoproteomics reveals that the hVPS34 regulated SGK3 kinase specifically phosphorylates endosomal proteins including Syntaxin-7, Syntaxin-12, RFIP4 and WDR44.

Malik Nazma N Nirujogi Raja S RS Peltier Julien J Macartney Thomas T Wightman Melanie M Prescott Alan R AR Gourlay Robert R Trost Matthias M Alessi Dario R DR Karapetsas Athanasios A

The Biochemical journal 20191001 20

The serum- and glucocorticoid-regulated kinase (SGK) isoforms contribute resistance to cancer therapies targeting the PI3K pathway. SGKs are homologous to Akt and these kinases display overlapping specificity and phosphorylate several substrates at the same residues, such as TSC2 to promote tumor growth by switching on the mTORC1 pathway. The SGK3 isoform is up-regulated in breast cancer cells treated with PI3K or Akt inhibitors and recruited and activated at endosomes, through its phox homology ...[more]

PMID: 31665227

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