Protein Distribution in Human Endothelial Cells in Primary Culture Studied by Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophores

 

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The surface structure and protein composition of cultured human endothelial cells were examined by lactoperoxidase catalyzed iodonation followed by SDS-PAGE of the cells. Five major protein bands (MW 224.000, 187.000, 70.000, 52.000 and 42.000) and several minor bands were seen. No differences in the protein pattern were observed between samples from confluent and nonconfluent cultures. In contrast, PAS staining of the gels revealed no glycoprotein bands unless the cells had grown to confluency. Then PAS staining revealed three bands of MW 240.000, 208.000 and 145.000. The fire one may represent fibronectin. The radioavtive iodine was associated with proteins in the 230.000, 145.000, 70.000, 55.000 and 45.000 MW regions. The first two regions showed iodination only in samples from confluent cultures. 33% of the acid-hydrolyzable sialic acid was liberated after neuraminidase treatment of the cells. No difference in the protein or glycoprotein pattern was seen after SDS-PAGE of neuraminidase-treated cells. In conclusion, four of the protein bands were susceptible to iodination, indicating an external localization in the plasma membrane. Two of these were iodinated only when cells had grown to confluency.