SAS Activators

Chemical activators of the protein kinase A (PKA) can initiate a cascade of phosphorylation events that regulate various cellular functions. Forskolin, by elevating cyclic AMP (cAMP) levels, can directly activate PKA. The increased cAMP serves as a second messenger that binds to the regulatory subunits of PKA, causing a conformational change that releases the catalytic subunits. These active catalytic subunits then phosphorylate target proteins, which may include the protein kinase A.

Engagement of protein kinase C (PKC) by Phorbol 12-myristate 13-acetate (PMA) also contributes to the phosphorylation and subsequent activation of the protein kinase A. PMA-activated PKC can phosphorylate specific serine or threonine residues on target proteins, including protein kinase A if it is within the PKC signaling pathway. Staurosporine and Bisindolylmaleimide I, under certain conditions, can also activate PKC, further enhancing the phosphorylation and activation of protein kinase A. On the other hand, Ionomycin, by raising intracellular calcium levels, can activate calcium-dependent protein kinases, which may phosphorylate and activate protein kinase A as part of the calcium-mediated signaling process. In contrast, Okadaic Acid, Calyculin A, and Lithium Chloride indirectly maintain the phosphorylation state of protein kinase A by inhibiting protein phosphatases that would otherwise dephosphorylate and deactivate it, thus ensuring its continued activity.