There was an error published in J. Cell Sci. 129, 2213-2223.In Fig. 4A, a statement that duplicate α-tubulin blots are shown for Mcl-1 and Bok, and for caspase-3 and Bax, because the same membranes were probed for these proteins, was inadvertently omitted from the legend.The authors apologise to the readers for any confusion that this error might have caused. 3054

There was an error published in J. Cell Sci. 129, 2213-2223.In Fig. 4A, a statement that duplicate α-tubulin blots are shown for Mcl-1 and Bok, and for caspase-3 and Bax, because the same membranes were probed for these proteins, was inadvertently omitted from the legend.The authors apologise to the readers for any confusion that this error might have caused.

Central to intrinsic apoptosis signaling is the release of cytochrome c from mitochondria, which depends on the pro-apoptotic effector proteins Bax, Bak or Bok. These pore-forming effector proteins share four Bcl-2 homology (BH) domains, a functionally essential and conserved sequence of hydrophobic amino acids in their BH3-domain and a C-terminal transmembrane-domain whose specific function remains rather unknown. To elucidate the molecular basis of Bok-mediated apoptosis we analyzed apoptosis induction by transmembrane-domain deficient BokΔTM compared to the respective Bax and Bak proteins and proteins in which the first leucine in the BH3-stretch was mutated to glutamic acid. We show that deletion of the C-terminal transmembrane-domain reduces the pro-apoptotic function of each protein. Mutation of the first leucine in the BH3-domain (L78E) blocks activity of Bak, while mutation of the homologue residues in Bax or Bok (L63E and L70E respectively) does not affect apoptosis induction. Unexpectedly, combined mutation of the BH3-domain and deletion of the transmembrane-domain enhances the pro-apoptotic activity of Bok(L70E)ΔTM by abolishing the interaction with anti-apoptotic proteins, especially the primary Bok-inhibitory protein Mcl-1. These results therefore suggest a specific contribution of the transmembrane-domain to the pro-apoptotic function and interaction of Bok.

cGMP is an important signalling molecule in humans. Fluorescent cGMP biosensors have emerged as powerful tools for the sensitive analysis of cGMP pathways at the single-cell level. Here, we briefly outline cGMP's multifaceted role in (patho)physiology and pharmacotherapy. Then we summarise what new insights cGMP imaging has provided into endogenous cGMP signalling and drug action, with a focus on the cardiovascular system. Indeed, the use of cGMP biosensors has led to several conceptual advances, such as the discovery of local, intercellular and mechanosensitive cGMP signals. Importantly, single-cell imaging can provide valuable information about the heterogeneity of cGMP signals within and between individual cells of an isolated cell population or tissue. We also discuss current challenges and future directions of cGMP imaging, such as the direct visualisation of cGMP microdomains, simultaneous monitoring of cGMP and other signalling molecules and, ultimately, cGMP imaging in tissues and animals under close-to-native conditions.

Declaration of transparency and scientific rigourThis Declaration acknowledges that this paper adheres to the principles for transparent reporting and scientific rigour of preclinical research as stated in the BJP guidelines for Design and Analysis, and Animal Experimentation, and as recommended by funding agencies, publishers and other organisations engaged with supporting research. Data availability statementThe data that support the findings of this study are available from the corresponding author upon reasonable request. Some data may not be made available because of privacy or ethical restrictions.