β1-6 branching of N-linked carbohydrate is associated with K-ras mutation in human colon carcinoma cell lines
Here the K-ras genotypes of nine colon carcinoma cell lines are compared to the protein glycosylation patterns found in these cells. By a variety of methodologies utilizing lectins to probe carbohydrate structure, we find evidence that five out of six cell lines having K-ras mutations have elevated amounts of beta 1-6 branching at the trimannosyl core of N-linked carbohydrate. None of the three K-ras wild type cell lines assayed have evidence of elevated beta 1-6 branching. In five out of five cell lines examined, the amount of beta 1-6 branching correlates with the extent of cellular ras-GTP elevation and supports the hypothesis that expression of beta 1-6 branching in colon carcinoma cell lines is quantitatively linked to K-ras activation. These results are discussed in the context of the ras-signalling pathway.