Distinct requirements for intra-ER sorting and budding of peroxisomal membrane proteins from the ER

During de novo peroxisome biogenesis, importomer complex proteins sort via two preperoxisomal vesicles (ppVs). However, the sorting mechanisms segregating peroxisomal membrane proteins to the preperoxisomal endoplasmic reticulum (pER) and into ppVs are unknown. We report novel roles for Pex3 and Pex19 in intra–endoplasmic reticulum (ER) sorting and budding of the RING-domain peroxins (Pex2, Pex10, and Pex12). Pex19 bridged the interaction at the ER between Pex3 and RING-domain proteins, resulting in a ternary complex that was critical for the intra-ER sorting and subsequent budding of the RING-domain peroxins. Although the docking subcomplex proteins (Pex13, Pex14, and Pex17) also required Pex19 for budding from the ER, they sorted to the pER independently of Pex3 and Pex19 and were spatially segregated from the RING-domain proteins. We also discovered a unique role for Pex3 in sorting Pex10 and Pex12, but with the docking subcomplex. Our study describes an intra-ER sorting process that regulates segregation, packaging, and budding of peroxisomal importomer subcomplexes, thereby preventing their premature assembly at the ER.     

ALDH3A1 Plays a Functional Role in Maintenance of Corneal Epithelial Homeostasis

Aldehyde dehydrogenase 1A1 (ALDH1A1) and ALDH3A1 are corneal crystallins. They protect inner ocular tissues from ultraviolet radiation (UVR)-induced oxidative damage through catalytic and non-catalytic mechanisms. Additionally, ALDH3A1 has been postulated to play a regulatory role in the corneal epithelium based on several studies that report an inverse association between ALDH3A1 expression and corneal cell proliferation. The underlying molecular mechanisms and the physiological significance of such association remain poorly understood. In the current study, we established Tet-On human corneal epithelial cell (hTCEpi) lines, which express tetracycline-inducible wild-type (wt) or catalytically-inactive (mu) ALDH3A1. Utilizing this cellular model system, we confirmed that human ALDH3A1 decreases corneal cell proliferation; importantly, this effect appears to be partially mediated by its enzymatic activity. Mechanistically, wt-ALDH3A1, but not mu-ALDH3A1, promotes sequestering of tumor suppressor p53 in the nucleus. In the mouse cornea, however, augmented cell proliferation is noted only in Aldh1a1^-/-/3a1^-/- double knockout (DKO) mice, indicating in vivo the anti-proliferation effect of ALDH3A1 can be rescued by the presence of ALDH1A1. Interestingly, the hyper-proliferative epithelium of the DKO corneas display nearly complete loss of p53 expression, implying that p53 may be involved in ALDH3A1/1A1-mediated effect. In hTCEpi cells grown in high calcium concentration, mRNA levels of a panel of corneal differentiation markers were altered by ALDH3A1 expression and modulated by its enzyme activity. In conclusion, we show for the first time that: (i) ALDH3A1 decreases corneal epithelial proliferation through both non-enzymatic and enzymatic properties; (ii) ALDH1A1 contributes to the regulation of corneal cellular proliferation in vivo; and (iii) ALDH3A1 modulates corneal epithelial differentiation. Collectively, our studies indicate a functional role of ALDH3A1 in the maintenance of corneal epithelial homeostasis by simultaneously modulating proliferation and differentiation through both enzymatic and non-enzymatic mechanisms.     

Proteomic analysis of Bacillus subtilis strains engineered for improved production of heterologous proteins

The use of bacterial systems for recombinant protein production has advantages of simplicity, time and cost over competing systems. However, widely used bacterial expression systems (e.g. Escherichia coli, Pseudomonas fluorescens) are not able to secrete soluble proteins directly into the culture medium. This limits yields and increases downstream processing time and costs. In contrast, Bacillus spp. secrete native enzymes directly into the culture medium at grams‐per‐litre quantities, although the yields of some recombinant proteins are severely limited. We have engineered the Bacillus subtilis genome to generate novel strains with precise deletions in the genes encoding ten extracytoplasmic proteases that affect recombinant protein secretion, which lack chromosomal antibiotic resistance genes. The deletion sites and presence of single nucleotide polymorphisms were confirmed by sequencing. The strains are stable and were used in industrial‐scale fermenters for the production of the Bacillus anthracis vaccine protein, protective antigen, the productivity of which is extremely low in the unmodified strain. We also show that the deletion of so‐called quality control proteases appears to influence cell‐wall synthesis, resulting in the induction of the cell‐wall stress regulon that encodes another quality control protease.     

Review: role of carbon sources for in vitro plant growth and development

In vitro plant cells, tissues and organ cultures are not fully autotrophic establishing a need for carbohydrates in culture media to maintain the osmotic potential, as well as to serve as energy and carbon sources for developmental processes including shoot proliferation, root induction as well as emission, embryogenesis and organogenesis, which are highly energy demanding developmental processes in plant biology. A variety of carbon sources (both reducing and non-reducing) are used in culture media depending upon genotypes and specific stages of growth. However, sucrose is most widely used as a major transport-sugar in the phloem sap of many plants. In micropropagation systems, morphogenetic potential of plant tissues can greatly be manipulated by varying type and concentration of carbon sources. The present article reviews the past and current findings on carbon sources and their sustainable utilization for in vitro plant tissue culture to achieve better growth rate and development.     

Inhibitory effects of superoxide dismutase 3 on IgE production in B cells

Immunoglobulin E (IgE) functions as a first-line defense against parasitic infections. However, aberrant production of IgE is known to be associated with various life-threatening allergic diseases. Superoxide dismutase 3 (SOD3) has been found to suppress IgE in various allergic diseases such as allergic conjunctivitis, ovalbumin-induced allergic asthma, and dust mite-induced atopic dermatitis-like skin inflammation. However, the role of SOD3 in the regulation of IgE production in B cells remains elusive. In this study, we investigated the effect of SOD3 on LPS/IL-4 and anti-CD40/IL-4-mediated secretion of IgE in murine B cells. Our data showed that SOD3 can suppress both LPS/IL-4 and antiCD40/IL-7-induced IgE secretion in B cells isolated from both wild-type (SOD3^+/+) and SOD3 knock-out (SOD3^?/?) mice. Interestingly, B cells isolated from SOD3^?/? mice showed higher secretion of IgE, whereas, the use of DETCA, a known inhibitor of SOD3 activity, reversed the inhibitory effect of SOD3 on IgE production. Similarly, SOD3 was found to reduce the proliferation, IgE isotype switch, ROS level, and CCL17 and CCL22 productions in B cells. Furthermore, SOD3 was found to suppress both LPS/IL-4 and anti-CD40/IL-4-mediated activation of downstream signaling such as JAK1/JAK3, STAT6, NF-κB, p38, and JNK in B cells. Taken together, our data showed that SOD3 can be used as an alternative therapy to restrict IgE-mediated allergic diseases.