Progress toward sourcing plants for new bioconjugation tools: a screening evaluation of a model peptide ligase using a synthetic precursor.

In the present study, leaves from 39 phylogenetically distant plant species were sampled and screened for asparaginyl endopeptidase ligase activity using mass spectrometry to test the generality of peptide ligases in plants. A modified version of the sunflower trypsin inhibitor-1 precursor was used as the substrate for reactions with leaf crude extracts and protein fractions. Masses consistent with products of asparaginyl endopeptidase activities that cleave and ligate the substrate into cyclic peptide following the reactions were detected in 8 plants: Nerium oleander and Thevetia peruviana of the family Apocynaceae; Bauhinia variegata, Dermatophyllum secundiflorum, Pithecellobium flexicaule, and Prosopis chilensis of the family Fabaceae; Morus alba of the family Moraceae; and Citrus aurantium of the family Rutaceae. This screening result represents a 20% hit rate for finding asparaginyl endopeptidase ligase activity from the arbitrary plants sampled. Analysis following a 2-h reaction of the substrate with the crude extract of D. secundiflorum leaves showed that the yield of cyclic peptide remained stable around 0.5 ± 0.1% of the substrate over the course of the reaction.

Induction of cardiomyocyte proliferation and angiogenesis protects neonatal mice from pressure overload-associated maladaptation.

Cardiac pressure overload (for example due to aortic stenosis) induces irreversible myocardial dysfunction, cardiomyocyte hypertrophy and interstitial fibrosis in patients. In contrast to adult, neonatal mice can efficiently regenerate the heart after injury in the first week after birth. To decipher whether insufficient cardiac regeneration contributes to the progression of pressure overload dependent disease, we established a transverse aortic constriction protocol in neonatal mice (nTAC). nTAC in the non-regenerative stage (at postnatal day P7) induced cardiac dysfunction, myocardial fibrosis and cardiomyocyte hypertrophy. In contrast, nTAC in the regenerative stage (at P1) largely prevented these maladaptive responses and was in particular associated with enhanced myocardial angiogenesis and increased cardiomyocyte proliferation, which both supported adaptation during nTAC. A comparative transcriptomic analysis between hearts after regenerative versus non-regenerative nTAC suggested the transcription factor GATA4 as master regulator of the regenerative gene-program. Indeed, cardiomyocyte specific deletion of GATA4 converted the regenerative nTAC into a non-regenerative, maladaptive response. Our new nTAC model can be used to identify mediators of adaptation during pressure overload and to discover novel potential therapeutic strategies.