DE-NOVO SYNTHESIS AND SECRETION OF A 36-KD PROTEIN BY CELLS THAT FORMLUPUS INCLUSIONS IN RESPONSE TO ALPHA-INTERFERON

In response to the pure recombinant human alpha-IFN, IFLrA, Raji and D audi were the only two cell lines among 19 human lymphoblastoid cell l ines tested that formed the human lupus inclusions (LI) to a high freq uency, Raji, Daudi, and five other cell lines were examined for protei n changes that might accompany LI formation. Their selection was based upon T or B origin, association with Epstein-Barr virus, and ability to form LI. A trace protein of an estimated molecular mass of 36 kD (p 36) and an isoelectric point of 5.6 was detected on two-dimensional ge ls only of alpha-IFN-treated Raji and Daudi cells. Gamma-IFN did not i nduce p36 or LI in any of these seven cell lines. In Daudi cells p36 a nd LI formed simultaneously in response to IFLrA, and persisted until the alpha-IFN-induced death of the culture. In Raji cells, p36 and LI appearance and disappearance coincided with the addition and removal o f alpha-IFN. Fractionation of Raji cells with nonionic-detergent buffe r placed p36 with the inclusions in the cytoplasmic supernatant. With detergent free buffer p36 and LI were distributed evenly between the n uclear and cytoplasmic fractions. Pulse-chase experiments revealed tha t p36 was secreted. The de novo synthesis of p36 with alpha-IFN treatm ent was shown by labeling the cell proteins with [S-35] methionine bef ore and after the addition of alpha-IFN. These results along with prev ious results on the de novo synthesis of LI in the endoplasmic reticul um (which is involved in the processing and secretion of proteins) sug gest a role for LI in the synthesis and secretion of p36.