Alkalinization of the lysosomes is correlated with ras transformation of murine and human fibroblasts. |
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Authors: | L W Jiang V M Maher J J McCormick M Schindler |
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Affiliation: | Department of Biochemistry, Michigan State University, East Lansing 48824-1316. |
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Abstract: | The pH of the intralysosomal compartment of fibroblasts in culture was monitored by measuring the fluorescence emission intensity at 530 nm of fluid phase pinocytosed fluorescein-conjugated dextrans (FITC-dextrans) excited at 488 and 457 nm. Following the procedure of Ohkuma and Poole (Ohkuma, S., and Poole, B. (1978) Proc. Natl. Acad. Sci. U. S. A. (1978) 75, 3327-3331), a relationship was established between the fluorescence emission intensity of the FITC-dextrans and pH. This correlation was used to determine the intralysosomal apparent pH (pHapp) of a series of fibroblast cultures. The mean intralysosomal pHapp values of nontransformed mouse 3T3 fibroblasts and an infinite life-span human fibroblast cell strain, designated MSU-1.1, was 5.0. In distinction that of 3T3 fibroblasts transformed to the malignant state by Kirsten murine sarcoma virus and MSU-1.1 cells transformed by transfection of the v-Ki-ras or T24 H-ras oncogene was 6.1. These measurements suggest that ras transformation results in a significant perturbation of lysosomal pH. |
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