Expression of the plasma membrane proteolipid in mouse neuroblastoma cells: transient increase in synthesis during differentiation with N6,O2-dibutyryl adenosine 3',5'-cyclic monophosphate.

We have examined the regulation of plasma membrane proteolipid (PM-PLP) synthesis and steady-state levels in mouse NB2a/d1 neuroblastoma cells during differentiation with dibutyryl cyclic AMP (dbcAMP) and retinoic acid (RA), agents which have been previously shown to induce the elaboration of exclusively axonal or dendritic neurites, respectively. We report that a PM-PLP-immunoreactive species is expressed by this neuroblastoma cell line, and that its expression is regulated by specific states of differentiation. Differentiation of cells with dbcAMP was accompanied by an initial 2-fold increase in this PM-PLP immunoreactive species at 24 h after treatment, which returned to control levels by 96 h after treatment. By contrast, no significant increase in synthesis was detected when cells were treated with RA. Protein blot analysis of PM-PLP in dbcAMP-treated cells indicated that there was little change in its steady-state level until 96 h following treatment, at which time a reduction of 40% was observed. Throughout induced differentiation with dbcAMP, NB2a/d1 cells continued to express a PM-PLP-immunoreactive species which comigrated on immunoblot analysis with PM-PLP form characteristic of embryonic brain (14-16 kDa), and apparently did not express the PM-PLP form characteristic of adult brain (18 kDa).