Transcriptional profiling of skeletal muscle tissue from two breeds of cattle

We used a 9.6 K cattle muscle/fat cDNA microarray to study gene expression differences between the longuissimus dorsi (LD) muscle of Japanese Black (JB) and Holstein (HOL) cattle. JB cattle exhibit an unusual ability to accumulate intramuscular adipose tissue with fat melting points lower than that in other breeds. The LD biopsies from three JB (Tajima strain) and three HOL animals were used in this breed comparison. Seventeen genes were identified as preferentially expressed in LD samples from JB and seven genes were found to be expressed more highly in HOL. The expression of six selected differentially expressed genes was confirmed by quantitative real-time PCR. The genes more highly expressed in JB are associated with unsaturated fatty acid synthesis, fat deposition, and the thyroid hormone pathway. These results are consistent with the increased amounts and proportions of monounsaturated fatty acids observed in the muscle of JB animals. By discovering as yet uncharacterized genes that are differentially regulated in this comparison, the work may lead us to a better understanding of the regulatory pathways involved in the development of intramuscular adipose tissue.     

Novel oxime and oxime ether derivatives of 12,14-dichlorodehydroabietic acid: design, synthesis, and BK channel-opening activity

Oxime ether derivatives of the benzylic ketone of 12,14-dichlorodehydroabietic acid (diCl-DHAA, 4b) were synthesised, and their BK channel-opening activity was evaluated in an assay system of CHO-K1 cells expressing hBKalpha channels. Oxime ether structure on the B ring of diCl-DHAA significantly increased the BK channel-opening activity.     

Overexpression of AtMHX in tobacco causes increased sensitivity to Mg<Superscript>2+</Superscript>, Zn<Superscript>2+</Superscript>, and Cd<Superscript>2+</Superscript> ions,induction of V-ATPase expression,and a reduction in plant size

AtMHX is a vacuolar transporter encoded by a single gene in Arabidopsis. Electrophysiological analysis showed that it exchanges protons with Mg²⁺, Zn²⁺, and Fe²⁺ ions. The physiological impact of AtMHX was examined so far only in tissue-culture grown seedlings of tobacco plants overexpressing this transporter. Here we investigated the impact of AtMHX on growth, response to different metals, and metal accumulation of mature tobacco plants, as well as Arabidopsis plants in which we overexpressed this transporter. The analyses were carried out in hydroponic growth-systems, in which the mineral composition could be effectively controlled, and the metal content of roots could be examined. Transformed tobacco plants showed necrotic lesions and apical burnings upon growth with increased levels of Mg²⁺, Zn²⁺, and Cd²⁺ ions. This suggested that AtMHX can carry in planta not only Mg²⁺ and Zn²⁺ ions, as previously deduced based on observations in tissue-culture, but also Cd²⁺ ions. Transformed plants of both tobacco and Arabidopsis showed a reduction in plant size. However, the overall response of Arabidopsis to AtMHX overexpression was minor. No change was detected in the mineral content of any organ of the transgenic tobacco or Arabidopsis plants. The necrotic lesions in tobacco resembled those seen in plants with perturbed proton balancing, raising the assumption that AtMHX can affect the proton homeostasis of cells. In agreement with this assumption, the transformed tobacco plants had increased expression and activity of the vacuolar H⁺-ATPase. The relative significance of AtMHX for metal and proton homeostasis still has to be elucidated.     

Stress-induced polyubiquitination of proteasomal ubiquitin receptors targets the proteolytic complex for autophagic degradation

Ubiquitin (Ub) is a small protein (8 kDa) found in all eukaryotic cells, which is conjugated covalently to numerous proteins, tagging them for recognition by a downstream effector. One of the best characterized functions of Ub is targeting proteins for either selective degradation by the proteasome, or for bulk degradation by the autophagy-lysosome system. The executing arm of the UPS is the 26S proteasome, a large multicatalytic complex. While much is known about the synthesis and assembly of the proteasome's subunits, the mechanism(s) underlying its removal has remained obscure, similar to that of many other components of the ubiquitin-proteasome system. Our recent study identified autophagy as the degrading mechanism for the mammalian proteasome, mostly under stress conditions. Amino acid starvation induces specific ubiquitination of certain 19S proteasomal subunits that is essential for its binding to SQSTM1/p62, the protein that shuttles the ubiquitinated proteasome to the autophagic machinery. SQSTM1 delivers ubiquitinated substrates for proteasomal degradation via interaction of its PB1 domain with the 19S proteasomal subunit PSMD4/Rpn10, in situations where the proteasome serves as a “predator." In contrast, we found that the UBA domain of SQSTM1 is essential for its interaction with the ubiquitinated proteasome and its delivery to the autophagosome, rendering the proteasome a “prey.”     

TRP gating is linked to the metabolic state and maintenance of the Drosophila photoreceptor cells

The Drosophila light-activated channel TRP is the founding member of a large and diverse family of channel proteins that is conserved throughout evolution. In spite of much progress, the gating mechanism of TRP channels is still unknown. However, recent studies have shown multi-faceted functions of the Drosophila light-sensitive TRP channel that may shed light on TRP gating. Accordingly, metabolic stress, which leads to depletion of cellular ATP, reversibly activates the Drosophila TRP and TRPL channels in the dark in a constitutive manner. In several Drosophila mutants, constitutive activity of TRP channels lead to a rapid retinal degeneration in the dark, while genetic elimination of TRP protects the cells from degeneration. Additional studies have shown that TRPL translocates in a light-dependent manner between the signaling membranes and the cell body. This light-activated translocation is accompanied by reversible morphological changes leading to partial and reversible collapse of the microvillar signaling membranes into the cytosol, which allows turnover of signaling molecules. These morphological changes are also blocked by genetic elimination of TRP channels. The link of TRP gating to the metabolic state and maintenance of cells makes cells expressing TRP extremely vulnerable to metabolic stress via a mechanism that may underlie retinal degeneration and neuronal cell death upon malfunction.