Phosphorylation and dephosphorylation of hormone‐sensitive lipase Interactions between the regulatory and basal phosphorylation sites

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Abstract
Phosphorylation of the basal site with glycogen synthase kinase‐4 enhanced the rate of phosphorylation of the regulatory site by cyclic AMP‐dependent protein kinase 1.7‐fold. In contrast, the phosphorylation state of the regulatory site did not affect the rate of phosphorylation of the basal site with glycogen synthase kinase‐4. The rate of dephosphorylation of either the regulatory or the basal phosphorylation site by protein phosphatase‐1, 2A or 2C was independent of the phosphorylation state of the other site. These results suggest that the basal phosphorylation site could play an indirect role in the control of the hormone‐sensitive lipase activity in the adipocyte by functioning as a recognition site for the cyclic AMP‐dependent protein kinase in the phosphorylation of the activity‐controlling regulatory phosphorylation site in response to lipolytic hormones.