The focus of this project is to better elucidate the possible involvement of transmembrane signal transmission systems in the regulation of cell growth, in malignant transformation, and in cellular resistance to chemotherapeutic drugs. Studies were carried out to examine the interrelationship between the biological effects and domain structure of protein kinase C epsilon (PKC epsilon). A series of NIH 3T3 cell lines were created, each overexpressing a different truncated epitope-tagged version of PKC epsilon. PKC epsilon e was found to localize to the Golgi network via its zinc finger domain, and both the PKC epsilon holoenzyme and its zinc finger region were observed to modulate Golgi function. Overexpression of either holo PKC epsilon or the zinc finger domain resulted in inhibition of Golgi-specific glycosaminlglycan sulfation. Sulfate uptake also was significantly decreased in cells expressing either the zinc finger fragment or holo PKC epsilon. These studies indicate that PKCn may be involved in regulating Golgi-related processes, and suggest that PKC domains other than the kinase domain also may have biological activity. Previous studies established that PKC can act to regulate sodium- dependent phosphate transport and that the normal function of the gibbon ape leukemia virus receptor (GLVR1) is to serve as a Na-Pi transporter. Our results now indicate that the amphotropic murine leukemia virus (MuLV) receptor (termed EAR) also functions as a Na-Pi transporter. There are, however, differences between EAR- and GLVR1- specific Pi transport. EAR exhibits a lower affinity for Pi, but a higher Vmax than GLVR1. In addition, EAR-, but not GLVR1-, mediated Na-Pi uptake is stimulated by PKC. Earlier studies demonstrated a deficiency of cAMP-dependent protein kinase (PKA) in fibroblasts isolated from patients with psoriasis. Results indicate that there is an altered phosphorylated form of the RII regulatory subunit of PKA present in psoriatic cells which is characterized by a decrease in cAMP binding and by modification to a form detected as a second unique spot by two-dimensional gel electrophoresis. Retinoic acid treatment of the psoriatic cells resulted in the disappearence of this unique phosphorylated form of RII.
