11-cis-retinal and Lymphoma

Topics: Adenosine Diphosphate Ribose; Adenylyl Cyclases; Animals; Bacterial Toxins; Cell Line; Chemical Phenomena; Chemistry; Cholera Toxin; GTP-Binding Proteins; Guanosine Triphosphate; Humans; Lymphoma; Membrane Proteins; Mice; Rhodopsin; Rod Cell Outer Segment; Saccharomyces cerevisiae; Transducin; Virulence Factors, Bordetella

GTP-binding proteins have been implicated as transducers of a variety of biological signaling processes. These proteins share considerable structural as well as functional homology. Due to these similarities, it was thought that a monoclonal antibody that inhibits the light activation of the rod outer segment GTP-binding protein, tranducin (Gt), might exert some functional effect upon the G proteins that regulate the adenylate cyclase system. Antibody 4A, raised against the alpha subunit of Gt, cross-reacted (by hybridization on nitrocellulose) with purified alpha subunits of other G proteins (Gi and Gs, regulatory guanyl nucleotide-binding proteins that mediate inhibition and stimulation of adenylate cyclase, respectively) as long as they were not denatured. This antibody, which interferes with rod outer segment cGMP phosphodiesterase activation by blocking interaction between rhodopsin and Gt, also interfered with actions of both the stimulatory and inhibitory G proteins of adenylate cyclase from rat cerebral cortex membranes. Effects of monoclonal antibody (mAb) 4A were dose-dependent and not reversed by washing. mAb 4A also blocked the Gi-mediated inhibition of adenylate cyclase in the cyc- variant of S49 lymphoma and in doing so raised the level of adenylate cyclase activity in both the cyc- variant and the S49 wild type. There was no effect of mAb 4A on adenylate cyclase activity of the resolved catalytic subunit. These results suggest that the well known sequence homologies among the G proteins involved in cellular signal transduction may extend to the sites that interact with other members of signal-transducing cascades (receptors and effector molecules). Therefore, antibody 4A may serve as a useful tool to probe the similarities and differences among the various systems.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Adenylyl Cyclase Inhibitors; Adenylyl Cyclases; Animals; Antibodies, Monoclonal; Antibody Specificity; Cell Membrane; Cerebral Cortex; Enzyme Activation; Guanosine 5'-O-(3-Thiotriphosphate); Guanosine Triphosphate; Guanylyl Imidodiphosphate; Immunoblotting; Light; Lymphoma; Mice; Photoreceptor Cells; Pineal Gland; Rats; Rhodopsin; Rod Cell Outer Segment; Thionucleotides; Transducin; Tumor Cells, Cultured

Antibodies were made against synthetic peptides that correspond to cytoplasmic domains of rhodopsin, the photopigment protein of the retinal rod. These antipeptide antibodies recognized rhodopsin as detected by immunoblot analysis. Antibodies directed against the cytoplasmic loop between transmembrane domains 1 and 2, as well as those directed against the serine/threonine-rich region of the COOH terminus of bovine rhodopsin, also recognized purified beta-adrenergic receptor isolated from mouse S49 lymphoma cells. In addition, antibodies raised against membrane-associated rhodopsin recognized the beta-adrenergic receptor. Both the antipeptide and anti-rhodopsin antibodies were able to detect a 65-kDa protein band corresponding to the molecular weight of the beta-adrenergic receptor in membranes derived from human placenta, rat adipocytes, and S49 mouse lymphoma cells. Putative recognition sites for the rhodopsin antibodies on the beta-adrenergic receptor are identified, and the significance of the homology between the two proteins is discussed.

Topics: Adipose Tissue; Amino Acid Sequence; Animals; Antibodies; Cattle; Cytoplasm; Female; Humans; Lymphoma; Mice; Peptide Fragments; Placenta; Pregnancy; Rats; Receptors, Adrenergic, beta; Retinal Pigments; Rhodopsin; Rod Cell Outer Segment