p53 Induces skin aging by depleting Blimp1+ sebaceous gland cells.

p53 is an important inducer of organismal aging. However, its roles in the aging of skin remain unclear. Here we show that mice with chronic activation of p53 develop an aging phenotype in the skin associated with a reduction of subcutaneous fat and loss of sebaceous gland (SG). The reduction in the fat layer may result from the decrease of mammalian TOR complex 1 (mTORC1) activity accompanied by elevated expression of energy expenditure genes, and possibly as compensatory effects, leading to the elevation of peroxisome proliferator-activated receptor (PPAR)γ, an inducer of sebocyte differentiation. In addition, Blimp1(+) sebocytes become depleted concomitantly with an increase in cellular senescence, which can be reversed by PPARγ antagonist (BADGE) treatment. Therefore, our results indicate that p53-mediated aging of the skin involves not only thinning through the loss of subdermal fat, but also xerosis or drying of the skin through declining sebaceous gland activity.

At the roots of a never-ending cycle.

Recent studies have yielded a number of important insights into the mechanisms of hair follicle development and cycling and have highlighted the particularly important roles played by stem cells and Wnt signaling pathways.

Investigation of the biological mode of action of clerocidin using whole cell assays.

Clerocidin, a diterpenoid natural product, has been shown in vitro to inhibit DNA religation following cleavage by topoisomerase II. Herein, we characterize the efficacy and specificity of clerocidin in HeLa cells. Our results suggest that clerocidin recognizes topoisomerase II as its main intracellular target and binds to this enzyme prior to formation of the 'cleavable complex' with DNA. These pharmacological features attest to the promising chemotherapeutic potential of this natural product.

Gbetagamma-mediated regulation of Golgi organization is through the direct activation of protein kinase D.

We have shown previously that the betagamma subunits of the heterotrimeric G proteins regulate the organization of the pericentriolarly localized Golgi stacks. In this report, evidence is presented that the downstream target of Gbetagamma is protein kinase D (PKD), an isoform of protein kinase C. PKD, unlike other members of this class of serine/threonine kinases, contains a pleckstrin homology (PH) domain. Our results demonstrate that Gbetagamma directly activates PKD by interacting with its PH domain. Inhibition of PKD activity through the use of pharmacological agents, synthetic peptide substrates, and, more specifically, the PH domain of PKD prevents Gbetagamma-mediated Golgi breakdown. Our findings suggest a possible mechanism by which the direct interaction of Gbetagamma with PKD regulates the dynamics of Golgi membranes and protein secretion.

Regulation of Golgi structure through heterotrimeric G proteins.

We have previously shown that ilimaquinone (IQ), a marine sponge metabolite, causes complete vesiculation of the Golgi stacks. By reconstituting the IQ-mediated vesiculation of the Golgi apparatus in permeabilized cells, we now demonstrate that this process does not require ARF and coatomers, which are necessary for the formation of Golgi-derived COPI vesicles. We find that IQ-mediated Golgi vesiculation is inhibited by G alpha(s)-GDP and G alpha(i3)-GDP. Interestingly, adding betagamma subunits in the absence of IQ is sufficient to vesiculate Golgi stacks. Our findings reveal that IQ-mediated Golgi vesiculation occurs through activation of heterotrimeric G proteins and that it is the free betagamma, and not the activated alpha subunit, that triggers Golgi vesiculation.

Inhibition of tumor progression by suppression of stress protein GRP78/BiP induction in fibrosarcoma B/C10ME.

Stress protein GRP78/BiP is highly induced in progressively growing tumors and has recently been shown to exert a protective role against lysis by cytotoxic T cells and tumor necrosis factor in vitro. This raises the question whether the in vitro observed protective function of GRP78/BiP translates into the in vivo situation in which tumors grow progressively, killing the host. Herein we report that molecular inhibition of GRP78/BiP induction in the fibrosarcoma B/C10ME, while not affecting in vitro cell proliferation, causes a dramatic increase in apoptotic cell death upon Ca2+ depletion of the endoplasmic reticulum. When B/C10ME cells incapable of inducing GRP78/BiP are injected into mice, tumors are initially formed that, however, regress presumably due to a cytotoxic T-cell response demonstrable by a strong in vitro response to the tumor with spleen cells of regressor mice. Since sensitivity to apoptosis is key to tumor rejection, these results may point to new approaches to the therapy of cancer via regulation of stress protein GRP78/BiP.

Learned aversion to soiled bedding in male mongolian gerbils.

This study was designed to determine whether the conditioned aversion paradigm could be extended to aversion to soiled bedding in the male Mongolian gerbil. In Experiment 1, sixty subjects were exposed to a glass petri dish filed with soiled bedding placed in the center of a one-meter-square open field for two 5-min sessions 48 hours apart. Half of the subjects received an injection of lithium chloride immediately after session 1, while the rest received saline. The LiCl subjects learned to avoid the soiled bedding in session 2, as indicated by significantly longer latency to first approach and lower frequency of approach to the stimulus. Experiment 2 examined conditioned aversion to specific to soiled bedding. The research results demonstrate olfactory aversion of this type is possible in gerbils, and suggest that it may have an important influence on their social behavior.