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Oncogenic Mutations of KRAS Modulate Its Turnover by the CUL3/LZTR1 E3 ligase Complex

ABSTRACT: KRAS is a proto-oncogene encoding a small GTPase. Mutations contribute up to 30% of human solid tumours including lung adenocarcinoma, pancreatic and colorectal carcinomas. Most KRAS activating mutations interfere with GTP hydrolysis, essential for its role as a molecular switch, leading to alterations in their molecular environment and oncogenic signalling. Here, APEX-2 proximity labelling was used to profile the molecular environment of wild type and G12D, G13D and Q61H activating mutants of KRAS under both, starvation and stimulation conditions. We demonstrate by quantitative proteomics the presence of known interactors of KRAS including a-RAF and LZTR1, which varied in abundance with wildtype and KRAS mutants. Notably, the KRAS mutations G12D, G13D and Q61H abrogate association with LZTR1. Wildtype KRAS and LZTR1, as part of the CUL3 ubiquitin E3 ligase complex, affect each other’s protein stability.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Permanent Cell Line Cell

SUBMITTER: Svenja Hester

LAB HEAD: Andreas Damianou

PROVIDER: PXD029725 | Pride | 2024-03-06

REPOSITORIES: Pride

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			Action	DRS
	20210809_KRAS_ZhuLiang_WTvsMT_PLUS_PROTEOME.sps	Other
	HF528_MSQ1736_200820_AndreasD_10.raw	Raw
	HF528_MSQ1736_200820_AndreasD_11.raw	Raw
	HF528_MSQ1736_200820_AndreasD_12.raw	Raw
	HF528_MSQ1736_200820_AndreasD_13.raw	Raw

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Project description:The small GTPase KRAS transmits signals from cell surface receptors to various downstream signaling pathways, thereby regulating a multitude of cellular processes. Activating KRAS mutations occur in approximately 30% of human cancers and contribute to malignant transformation through constitutive activation of downstream signaling cascades. These mutations cluster in several hotspots, with codons 12 and 13 being most commonly. It has been suggested that the position and type of amino acid exchange influence the transforming capacity of mutant KRAS proteins. To address this hypothesis, we used MCF10A human mammary epithelial cells to establish isogenic cell lines that express eight different cancer-associated KRAS mutations (G12C, G12D, G12V, G13C, G13D, A18D, Q61H, K117N) at physiological levels, and investigated the biochemical and functional consequences of the different KRAS variants in vitro. In addition, selected effects were evaluated in comparison to cells that overexpress mutant KRAS. The overall effects of mutants expressed at normal levels were moderate compared to overexpressed variants, but allowed delineation of biological functions that were related to specific alleles rather than KRAS expression level. None of the mutations induced morphological changes or migratory abilities. KRAS-G12D, -G12V, -G13D, and -K117N were able to mediate EGF-independent proliferation, whereas anchorage-independent growth was primarily induced by the K117N and Q61H variants. Analysis of known RAS effectors showed that none of the mutations led to increased phosphorylation of ERK, PDK1, or AKT. Both codon 13 mutations were associated with increased EGFR expression, which was not seen with other variants. Finally, comparative gene expression analysis of MCF10A-G13D versus MCF10A-G12D revealed distinct transcriptional changes, such as enhanced cytokine and p53 signaling, upon G13D expression. Together, we describe a useful resource for investigating the function of multiple KRAS mutations and provide insights into the differential effects of these variants in MCF10A cells.

Project description:K-ras mutations are observed in around 40% human colorectal adenomas and carcinomas and contribute to the pathogenesis of human and rodent colorectal tumour formation. Previously, we developed and characterised a strain of transgenic mice with inducible intestinal epithelial expression of K-rasVal12 via a Cre/LoxP system. To evaluate the influence of mutant K-ras on carcinogen-induced colorectal tumourigenesis, we induced neoplastic alterations in the large intestines of wild-type and K-rasVal12 mice using the colon-selective carcinogen 1, 2-dimethylhydrazine (DMH), which has been widely used to study chemically induced colorectal tumours that are histopathologically similar to those observed in humans. K-rasVal12 expression significantly promoted DMH-induced colorectal tumourigenesis: the average life span of the mice decreased from 38.52Â±1.97 weeks for 40 wild-type mice to 32.42Â±2.17 weeks for 26 K-rasVal12 mice (mean+SEM, P<0.05) and the large intestinal tumours increased from 2.27Â±0.15 per wild-type mouse to 3.85Â±0.20 in K-rasVal12 mice (mean+SEM, P<0.01). Adenomas from DMH-treated K-rasVal12 mice showed significantly higher levels (10.9Â±1.69%) of Ki-67-positive proliferating cells compared with those from DMH-treated wild-type mice (7.77Â±1.15%) (mean+SD, P<0.01) and a mild increase in apoptotic nuclei staining for cleaved caspase-3 (1.94+0.51% compared with 1.15Â±0.34%, mean+SD, P<0.01). In the adenomas from DMH-treated K-rasVal12 mice, K-rasVal12 transgene recombination and expression were confirmed and shown to promote strong Erk and mild Akt activation compared with adenomas from DMH-treated wild-type mice. Microarray hybridization and cluster analysis demonstrated different expression profiles in adenomas from DMH-treated wild-type and DMH-treated K-rasVal12 mice, indicating involvement of different molecular mechanisms, but array-comparative genomic hybridisation analysis showed chromosome stability in both, with very few chromosome alterations observed in adenomas from either of the two groups. Taken together, these data show that mutant K-ras promotes DMH-induced colorectal tumourigenesis, conferring a proliferative effect, but does not alter chromosome stability in the tumours. This study has 7 samples analysed, 4 Kras mutants and 3 controls, on the Illumina Mouse-6 Beadchip array.

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Oncogenic Mutations of KRAS Modulate Its Turnover by the CUL3/LZTR1 E3 ligase Complex

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