More than four decades passed since sigma receptors were first
mentioned. Since then, existence of at least two receptor
subtypes and their tissue distributions have been proposed.
Nowadays, it is clear, that sigma receptors are unique ubiquitous
proteins with pluripotent function, which can interact with so
many different classes of proteins. As the endoplasmic resident
proteins, they work as molecular chaperones - accompany
various proteins during their folding, ensure trafficking of the
maturated proteins between cellular organelles and regulate their
functions. In the heart, sigma receptor type 1 is more dominant.
Cardiac sigma 1 receptors regulate response to endoplasmic
reticulum stress, modulates calcium signaling in cardiomyocyte
and can affect function of voltage-gated ion channels. They
contributed in pathophysiology of cardiac hypertrophy, heart
failure and many other cardiovascular disorders. Therefore,
sigma receptors are potential novel targets for specific treatment
of cardiovascular diseases.
Little data on the role played in vivo by chloroplast protein AtDeg2 as a chaperone is available. Therefore, we sought for chloroplast proteins protected from high irradiance-induced interprotein aggregation via disulphide bridges by AtDeg2 acting as a holdase. To reach this goal, we performed analyses which involved comparative diagonal electrophoreses of lysates of chloroplasts isolated from wild type (WT) plants and transgenic plants 35S:AtDEG2ΔPDZ1-GFP which expressed AtDeg2 lacking its chaperone activity but retaining the protease activity. The results of the analyses indicate that AtDeg2 acting as a holdase prevents a single chloroplast protein, i.e., the γ1 subunit of ATP synthase from long-term high irradiance-induced homodimerization mediated by disuplhide bridges and this allows us to better understand a complexity of physiological significance of AtDeg2 - the chloroplast protein of dual protease/chaperone activity.