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Introduction The expansion of atherosclerotic lesions and post-angioplasty restenosis result mostly from a change in the phenotype of medial vascular smooth muscle cells (VSMC). We have provided evidence in vivo and in vitro that the de novo expression Adenylyl Cyclase 8 (AC8) is critical for VSMC inflammation, migration, atherogenesis and neointima formation. This increase in AC expression initially appeared counterintuitive: increases in [cAMP]i have been shown to inhibit the migratory, proliferative and inflammatory properties of tdVSMC. We discovered that this AC8 is a family of short AC8 proteins, called AC8E-H, derived from AC8 RNA splice-variants. The global aim of the project is to determine whether AC8E-H are of potential value for treating tdVSMC-related vascular diseases. Objective As an initial approach, we aim at deciphering the molecular mechanism(s) leading AC8E-H to modulate VSMC properties and characterizing the integration of extracellular signals in tdVSMC expressing AC8E-H. Method FRET-based biosensor TEpacVV to image/compare cAMP responses in: – contractile vs AC8E-H-expressing tdVSMC; – HEK transfected cells where the AC8E-H and AC3 or AC6 are co-expressed. The mechanism of the effect of AC8E isoform on cAMP production was determined by biochemical approaches. Results Our data demonstrate a dominant-negative effect of AC8E on AC3 and AC6 function associated with a physical interaction between these two proteins, and they suggest that the AC8E-H-dependent decrease in cAMP synthesis is due, in part, to a loss of AC trafficking to the plasma membrane. In tdVSMC, AC8E would preferentially act on AC6-dependent cAMP production. Conclusion These short AC8 proteins act as dominant-negative regulators of cAMP production by a direct interaction with functional ACs. We are now identifying heterodimerization domain/motifs in AC8E in the prospect of disrupting this interaction in order to prevent tdVSMC-related pathological vascular remodelings. [ABSTRACT FROM AUTHOR]