Direct visualization of cGMP microdomains in adult cardiomyocytes

Results Cardiomyocytes were isolated from the transgenic mice expressing the cytosolic red cGES-DE5 sensor [1]. Using the previously established scanning ion conductance microscopy (SICM)/FRET method [2], local application of Atrial Natriuretic Peptide (ANP) at T-tubules and crests revealed the exclusive localization of guanylyl cyclase A (GC-A) in T-tubules. In contrast, guanylyl cyclase B (GC-B), the receptor for the C-type Natriuretic Peptide (CNP), was more evenly distributed across the membrane. Further, two differentially targeted cGMP sensors were generated. One of them was targeted to the caveolin-rich membrane microdomains via a palmitoylation and myristoylation motif (pmDE5) and another one to the sarcoplasmic reticulum by the fusion with phospholamban (DE5-PLN). FRET measurements in cardiomyocytes from these transgenic mice revealed close association of the GC-A with the caveolin-rich membrane microdomains, as well as a CNP, but not ANP-dependent regulation of cGMP levels at the sarcoplasmic reticulum.