Peroxisomes contribute to intracellular calcium dynamics in cardiomyocytes and non-excitable cells

Sargsyan Y, Bickmeyer U, Gibhardt CS, Streckfuss-Bomeke K, Bogeski I, Thoms S. Peroxisomes contribute to intracellular calcium dynamics in cardiomyocytes and non-excitable cells. Life science alliance. 2021;4(9).Peroxisomes communicate with other cellular compartments by transfer of various metabolites. However, whether peroxisomes are sites for calcium handling and exchange has remained contentious. Here we generated sensors for assessment of peroxisomal calcium and applied them for single cell-based calcium imaging in HeLa cells and cardiomyocytes. We found that peroxisomes in HeLa cells take up calcium upon depletion of intracellular calcium stores and upon calcium influx across the plasma membrane. Furthermore, we show that peroxisomes of neonatal rat cardiomyocytes and human induced pluripotent stem cell-derived cardiomyocytes can take up calcium. Our results indicate that peroxisomal and cytosolic calcium signals are tightly interconnected both in HeLa cells and in cardiomyocytes. Cardiac peroxisomes take up calcium on beat-to-beat basis. Hence, peroxisomes may play an important role in shaping cellular calcium dynamics of cardiomyocytes. © 2021 Sargsyan et al

Analysis of Menstrual Blood Stromal Cells Reveals SOX15 Triggers Oocyte-Based Human Cell Reprogramming

We acknowledge the assistance and support of Laboratory for Cell Reprogramming and BIONAND students, colleagues, and collaborators. We thank members of the LARCEL laboratory and Prof. J.B. Cibelli (Michigan State University) for comments, discussion, and support; Dr. Ariane Wittgreen for intellectual input and discussion; and Biobanco del Sistema Sanitario Pu´blico de Andalucı´a for karyotyping and teratoma assay service. The authors thankfully acknowledge the computer resources (IPA software) provided by the PAB (Andalusian Bioinformatics Platform) center located at the University of Malaga (www.scbi.uma.es).Supplemental Information can be found online at https://doi.org/10.1016/j.isci.2020.101376.Cell reprogramming has revolutionized cell and regenerative biology field. However, human iPS derivation remains inefficient and variable. A better knowledge of molecular processes and the rationale underlying the importance of somatic cell origin is crucial to uncover reprogramming mechanisms. Here, we analyze the molecular profile of different human somatic cell types. We show menstrual blood-derived stromal cells (MnSCs) have a distinct, reprogramming prone, profile, and we identify SOX15 from their oocyte-related signature as a prominent responsible candidate. SOX15 orchestrates an efficient oocyte-based reprogramming combination when overexpressed with the also oocyte-enriched histone chaperone ASF1A and OCT4 and, through specific mechanism, generates iPSCs with distinguishable pluripotent state that further present higher differentiation capacity than canonical iPSCs. Our work supports the presence of different pluripotency states in reprogramming and the importance of using metaphase-II oocyte and MnSCs information to provide alternative reprogramming combinations and, importantly, to improve and understand pluripotency acquisition.Ministerio de Economía y Competitividad Gobierno de España (MINECOSAF2015- 66105-R and RYC-2014-15410)Fundación Progreso y Salu

Yeast ubiquitin ligase Rsp5 contains nuclear localization and export signals

The Rsp5 ubiquitin ligase regulates numerous cellular processes. Rsp5 is mainly localized to the cytoplasm but nuclear localization was also reported. A potential nuclear export signal was tested for activity by using a GFP2 reporter. The 687-LIGGIAEIDI-696 sequence located in the Hect domain was identified as a nuclear export signal active in a Crm1-dependent manner, and its importance for the localization of Rsp5 was documented by using fluorescence microscopy and a lacZ-based reporter system. Analysis of the cellular location of other Rsp5 fragments fused with GFP2 indicated two independent potential nuclear localization signals, both located in the Hect domain. We also uncovered Rsp5 fragments that are important to targeting/tethering Rsp5 to various regions in the cytoplasm. The presented data indicate that Rsp5 ligase is a shuttling protein whose distribution within the cytoplasm and partitioning between cytoplasmic and nuclear locations is determined by a balance between the actions of several targeting sequences and domains