The hormonal family of vasoinhibins, which derive from the anterior pituitary hormone prolactin, are known for their inhibiting effects on blood vessel growth, vasopermeability, and vasodilation. As pleiotropic hormones, vasoinhibins act in multiple target organs and tissues. The generation, secretion, and regulation of vasoinhibins are embedded into the organizational principle of an axis, which integrates the hypothalamus, the pituitary, and the target tissue microenvironment. This axis is designated as the prolactin/vasoinhibin axis. Disturbances of the prolactin/vasoinhibin axis are associated with the pathogenesis of retinal and cardiac diseases and with diseases occurring during pregnancy. New phylogenetical, physiological, and clinical implications are discussed.

The Jun-N-terminal Kinase pathway (JNK), known also as stress activated protein kinase pathway (SAPK), is an eukaryotic evolutionarily conserved signaling pathway. From a purported evolutionarily "ancient" function as stress mediator, it evolved in multicellular eukaryotes to permanent roles in development, without leaving its original function. In Drosophila melanogaster, it is required for follicle cell morphogenesis, embryonic dorsal closure, pupal thoracic closure and genital disc rotation closure, all processes with requisite cell shape changes. Besides, it is activated during wound healing and in response to stress (UV irradiation, oxidative stress) where it may signal cell death or proliferation. Despite these varied roles, it has a conserved core of molecules that follow the MAPKKK/MAPKK/MAPK logic of mitogen activated protein kinases pathways. Regulation of the JNK pathway appears majorly negative, with phosphatases, transcription factors and proteins of novel structure "holding back" on JNK activation in different tissues. This particular mode of regulation may hark back to the pathway's origin as stress detector and responder, implying readiness to respond, from which the developmental roles may have evolved as conditions demanding obligate and predicted stress responses (i.e., embryonic dorsal closure viewed as a "wound of development").

SignificanceExporting bulky molecules poses challenges for cells, since the membrane vesicles that transport normal-sized molecules may not be sufficiently large. The protein Tango1 allows transport vesicles to grow much larger to accommodate bulky cargo. It has been puzzling why many smaller cargos also fail to be transported when Tango1 is absent. We show that this is because bulky cargos “clog up” the transport system, resulting in a general traffic jam. Once the blocking, large cargo is removed, the jam resulting from missing Tango1 is resolved, and other cellular stress signals also subside. However, structural defects in the transport system remain, showing that these are due to a direct requirement for Tango1, independent of its function in transport as such.

Dorsal closure is an epithelial remodeling process taking place during Drosophila embryogenesis. JNK signaling coordinates dorsal closure. We identify and characterize acal as a novel negative dorsal closure regulator. acal represents a new level of JNK regulation. The acal locus codes for a conserved, long, non-coding, nuclear RNA. Long non-coding RNAs are an abundant and diverse class of gene regulators. Mutations in acal are lethal. acal mRNA expression is dynamic and is processed into a collection of 50 to 120 bp fragments. We show that acal lies downstream of raw, a pioneer protein, helping explain part of raw functions, and interacts genetically with Polycomb. acal functions in trans regulating mRNA expression of two genes involved in JNK signaling and dorsal closure: Connector of kinase to AP1 (Cka) and anterior open (aop). Cka is a conserved scaffold protein that brings together JNK and Jun, and aop is a transcription factor. Misregulation of Cka and aop can account for dorsal closure phenotypes in acal mutants.

Plasma membranes fulfil many physiological functions. In polarized cells, different membrane compartments take on specialized roles, each being allocated correct amounts of membrane. The Drosophila tracheal system, an established tubulogenesis model, contains branched terminal cells with subcellular tubes formed by apical plasma membrane invagination. We show that apical endocytosis and late endosome‐mediated trafficking are required for membrane allocation to the apical and basal membrane domains. Basal plasma membrane growth stops if endocytosis is blocked, whereas the apical membrane grows excessively. Plasma membrane is initially delivered apically and then continuously endocytosed, together with apical and basal cargo. We describe an organelle carrying markers of late endosomes and multivesicular bodies (MVBs) that is abolished by inhibiting endocytosis and which we suggest acts as transit station for membrane destined to be redistributed both apically and basally. This is based on the observation that disrupting MVB formation prevents growth of both compartments.