Role of G-proteins in ciliary process adenylyl cyclase responses of the albino rabbit eye

The use of proteomics in ophthalmic research

The goal of molecular ophthalmology is the early detection and therapeutic treatment of eye disease. Genomic technologies have profoundly enhanced the discovery of ocular disease candidate genes. Proteomics, the protein cognate of genomic technology, offers a means to monitor changes in the expression of a given ocular protein(s) and its post-translational modification, identify novel therapeutic targets and evaluate pharmacological effects on a given metabolic pathway. Using both tissue and cultured cells, numerous laboratories have begun to catalogue changes in ocular protein expression in normal, diseased and ageing subjects. Herein, we review published proteomic literature in the broad context of ophthalmic diseases involving various tissues of the eye.

Endogenous ADP-ribosylation of a G(alpha i) protein in bovine ciliary body is stimulated by nitric oxide

Five ciliary body membrane proteins were labeled when incubated with (adenylate-32P)NAD. Nitric oxide donors stimulated the labeling of 64, 40, and 29-30 kDa proteins and inhibited that of 58 and 56 kDa proteins. The greatest influence of nitric oxide was on the 40 kDa protein: a 17-fold stimulation. Western blotting and immunoprecipitation with specific antibodies identified this protein as the alpha-subunit of G(i-1). Studies with inhibitors showed that the protein was mono-ADP-ribosylated. Treatment of (32P)NAD-labeled G(i-1) with Hg and analysis of the released radioactive material showed that the protein was ADP-ribosylated on a cysteine residue.

Endotoxins in cholera and pertussis toxins interfere with in vivo responses to these agents in the albino rabbit eye

Intravitreal injections of cholera or pertussis toxin (CTX or PTX, 0.5-1 microgram/eye) decreased intraocular pressure (IOP) up to 50% in the albino rabbit eye, which lasted up to six days. Both toxins were active on G-proteins as determined by in vitro and in vivo effects on ciliary process adenylyl cyclase activity and by ADP ribosylation of G-protein alpha-subunits with 32P-NAD. However, forty-two hours after toxin injection aqueous humor proteins increased from control levels of 0.8-1.2 mg/ml to 8-25 mg/ml. Both toxins contained 1-3 parts per thousand endotoxin sufficient to cause the IOP and aqueous humor protein responses observed. We conclude that the in vivo responses to intraocular CTX or PTX obtained from commercial sources may not provide unequivocal evidence for the role(s) of G-proteins in aqueous humor dynamics, and must be interpreted with caution.