Lipid rafts integrity is essential for prolactin-induced mitogenesis in mouse embryonic stem cells.

Embryonic stem cells, ESCs, retain the capacity to self-renew, yet, the protein machinery essential in maintaining this undifferentiated status remains largely undefined. Signalling interactions are initiated and enhanced at the plasma membrane lipid rafts, within constraints and regulations applied by the actin and tubulin cytoskeleton systems. First, we undertook a comprehensive approach using two-dimensional gel electrophoresis and mass spectrometry analysis combined with Western blotting and immunofluorescence analyses at the single cell level to compile the proteome profile of detergent-free preparations of lipid rafts of E14 mouse embryonic stem cells.

Nuclear Isoforms of Neurofibromin Are Required for Proper Spindle Organization and Chromosome Segregation.

Mitotic spindles are highly organized, microtubule (MT)-based, transient structures that serve the fundamental function of unerring chromosome segregation during cell division and thus of genomic stability during tissue morphogenesis and homeostasis. Hence, a multitude of MT-associated proteins (MAPs) regulates the dynamic assembly of MTs in preparation for mitosis. Some tumor suppressors, normally functioning to prevent tumor development, have now emerged as significant MAPs.

PKCε-dependent H-Ras activation encompasses the recruitment of the RasGEF SOS1 and of the RasGAP neurofibromin in the lipid rafts of embryonic neurons.

The spatial organization of plasma membrane proteins is a key factor in the generation of distinct signal outputs, especially for PKC/Ras/ERK signalling. Regulation of activation of the membrane-bound Ras, critical for neuronal differentiation and highly specialized functions, is controlled by exchanges in nucleotides catalyzed by nucleotide exchange factors (GEFs) for GTP loading and Ras activation, and by Ras GTPase Activated Proteins (RasGAPs) that lead to activation of the intrinsic GTPase activity of Ras and thus its inactivation. PKCs are potent Ras activators yet the mechanistic details of these interactions, or the involvement of specific PKC isoforms are now beginning to be addressed.

Nuclear import mechanism of neurofibromin for localization on the spindle and function in chromosome congression.

Neurofibromatosis type-1 (NF-1) is caused by mutations in the tumor suppressor gene NF1; its protein product neurofibromin is a RasGTPase-activating protein, a property that has yet to explain aneuploidy, most often observed in astrocytes in NF-1. Here, we provide a mechanistic model for the regulated nuclear import of neurofibromin during the cell cycle and for a role in chromosome congression. Specifically, we demonstrate that neurofibromin, phosphorylated on Ser2808, a residue adjacent to a nuclear localization signal in the C-terminal domain (CTD), by Protein Kinase C-epsilon (PKC-ε), accumulates in a Ran-dependent manner and through binding to lamin in the nucleus at G2 in glioblastoma cells.

Long-term changes in the ghrelin-CB1R axis associated with the maintenance of lower body weight after sleeve gastrectomy.

Objectives: In the hypothalamus, the molecular actions of receptors for growth hormone secretagogue (ghrelin) receptor-GHSR, leptin receptor-b (LEPRb), Melanocortin-4 receptor (MC4R) and Cannabinoid-1 receptor (CB1R) regulate energy homeostasis and body weight. We hypothesized that the acute loss of stomach tissue upon sleeve gastrectomy (SG), performed to treat obesity, imposes modulations on the expression of these receptors in the brain to sustain weight loss.

Methods: Rats, induced to obesity with high-fat diet were randomized to SG- or sham-operation groups and killed at 30 or 90 days post surgery, when the expression of Ghrl, Mboat4 and Cnr1 in the stomach, and Ghsr, Leprb, Mc4r and Cnr1 in distinct brain areas was assessed by reverse transcription-PCR and western blotting.