Nuclear Targeting of FBPase in HL-1 Cells is Controlled by Beta-1 Adrenergic Receptor-activated Gs Protein Signaling Cascade

Muscle fructose 1,6-bisphosphatase (FBPase), a well-known regulatory enzyme of glyconeogenic pathway has recently been found inside nuclei of several cell types (cardiomyocytes, smooth muscle cells, myogenic progenitor cells). This surprising finding raised a question concerning the role of FBPase in this compartment of the cell, and of the extracellular signals regulating nuclear transport of the enzyme. In the present paper we show that, in HL-1 cardiomyocyte cell line, the activity of adenylyl cyclase and cAMP-dependent protein kinase A is essential to nuclear import of FBPase. The import is also stimulated by isoproterenol (a nonselective beta-adrenergic receptors agonist) and inhibited by metoprolol (a selective beta1 antagonist), strongly suggesting that nucleo-cytoplasmic shuttling of FBPase is under the control of beta1-adrenergic receptor-dependent Gs protein signaling cascade.