Light and Gravity Effects on Adenine Nucleotide Content and Energy Charge in Maize Roots

Two millimeter apical segments of maize (cv. LG 11) primary roots were analysed in relation to the effects of light and gravity on adenine nucleotide content. Adenosine triphosphate (ATP) content is very sensitive to these stimuli. ATP levels are lower in roots exposed to light than in those kept in the dark. The energy charge (E.C.) decreases markedly after exposure to light and gravity. For the vertical roots E.C. is stable. Present data confirm the fact that light and gravity may act on cell metabolism, modifying the energy requirements. This will be discussed in relation to some hormone action

Discovery of a Highly Conserved Peptide in the Iron Transporter Melanotransferrin that Traverses an Intact Blood Brain Barrier and Localizes in Neural Cells

The blood-brain barrier (BBB) hinders the distribution of therapeutics intended for treatment of diseases of the brain. Our previous studies demonstrated that that a soluble form of melanotransferrin (MTf; Uniprot P08582; also known as p97, MFI2, and CD228), a mammalian iron-transport protein, is an effective carrier for delivery of drug conjugates across the BBB into the brain and was the first BBB targeting delivery system to demonstrate therapeutic efficacy within the brain. Here, we performed a screen to identify peptides from MTf capable of traversing the BBB. We identified a highly conserved 12-amino acid peptide, termed MTfp, that retains the ability to cross the intact BBB undigested, distribute throughout the parenchyma, and enter endosomes and lysosomes within neurons, astrocytes and microglia in the brain. This peptide may provide a platform for the transport of therapeutics to the CNS, and thereby offers new avenues for potential treatments of neuropathologies that are currently refractory to existing therapies

A Unique Carrier for Delivery of Therapeutic Compounds beyond the Blood-Brain Barrier

BACKGROUND: Therapeutic intervention in many neurological diseases is thwarted by the physical obstacle formed by the blood-brain barrier (BBB) that excludes most drugs from entering the brain from the blood. Thus, identifying efficacious modes of drug delivery to the brain remains a "holy grail" in molecular medicine and nanobiotechnology. Brain capillaries, that comprise the BBB, possess an endogenous receptor that ferries an iron-transport protein, termed p97 (melanotransferrin), across the BBB. Here, we explored the hypothesis that therapeutic drugs "piggybacked" as conjugates of p97 can be shuttled across the BBB for treatment of otherwise inoperable brain tumors. APPROACH: Human p97 was covalently linked with the chemotherapeutic agents paclitaxel (PTAX) or adriamycin (ADR) and following intravenous injection, measured their penetration into brain tissue and other organs using radiolabeled and fluorescent derivatives of the drugs. In order to establish efficacy of the conjugates, we used nude mouse models to assess p97-drug conjugate activity towards glioma and mammary tumors growing subcutaneously compared to those growing intracranially. PRINCIPAL FINDINGS: Bolus-injected p97-drug conjugates and unconjugated p97 traversed brain capillary endothelium within a few minutes and accumulated to 1-2% of the injected by 24 hours. Brain delivery with p97-drug conjugates was quantitatively 10 fold higher than with free drug controls. Furthermore, both free-ADR and p97-ADR conjugates equally inhibited the subcutaneous growth of gliomas growing outside the brain. Evocatively, only p97-ADR conjugates significantly prolonged the survival of animals bearing intracranial gliomas or mammary tumors when compared to similar cumulated doses of free-ADR. SIGNIFICANCE: This study provides the initial proof of concept for p97 as a carrier capable of shuttling therapeutic levels of drugs from the blood to the brain for the treatment of neurological disorders, including classes of resident and metastatic brain tumors. It may be prudent, therefore, to consider implementation of this novel delivery platform in various clinical settings for therapeutic intervention in acute and chronic neurological diseases

Développement de nouveaux vecteurs protéiniques pour le transport physiologique d’agents thérapeutiques vers le système nerveux central

Le système nerveux central (SNC) est un sanctuaire protégé par des barrières, dont la barrière hémato-encéphalique (BHE). L’existence de la BHE est liée à la nature spécifique des cellules endothéliales des capillaires cérébraux qui permettent l’accès au cerveau des éléments nutritifs nécessaires à la fonction et à la survie des cellules cérébrales. Mais ces propriétés entraînent l’impossibilité pour des composés thérapeutiques petits et grands d’atteindre le cerveau à des concentrations thérapeutiques. Diverses stratégies ont été envisagées afin d’augmenter la quantité et la concentration de ces composés dans le parenchyme cérébral. Le développement de nouvelles technologies associées à de nouveaux vecteurs peptidiques a pour but de faciliter le transport de composés actifs à travers la BHE pour atteindre des concentrations thérapeutiques dans le cerveau et traiter des maladies du SNC comme le cancer ou les maladies neurodégénératives. Dans cet article, le développement de nouveaux vecteurs peptidiques permettant le ciblage de médicaments au cerveau à l’aide d’approches physiologiques sera abordé. À côté de la technologie de plateforme Angiopep qui est en développement chez Angiochem Inc., actuellement la plus avancée car au stade des essais cliniques humains, la technologie développée par biOasis Technologies Inc., Transcend, utilisant la mélanotransferrine (MTf) pour le transport de produits biologiques, tels que des enzymes lysosomales et des anticorps, ainsi que d’autres technologies seront discutées

The Adenovirus E3-6.7K Protein Adopts Diverse Membrane Topologies following Posttranslational Translocation

The E3 region of adenovirus codes for several membrane proteins, most of which are involved in immune evasion and prevention of host cell apoptosis. We explored the topology and targeting mechanisms of E3-6.7K, the most recently described member of this group, by using an in vitro translation system supplemented with microsomes. Here, we present evidence that E3-6.7K, one of the smallest signal-anchor proteins known, translocates across the membrane of the endoplasmic reticulum in a posttranslational, ribosome-independent, yet ATP-dependent manner, reminiscent of the translocation of tail-anchored proteins. Our analysis also demonstrated that E3-6.7K could achieve several distinct topological fates. In addition to the previously postulated type III orientation (N-luminal/C-cytoplasmic, termed (Ntm)E3-6.7K), we detected a tail-anchored form adopting the opposite orientation (N-cytoplasmic/C-luminal, termed (Ctm)E3-6.7K) as well as the possibility of a fully translocated form (N and C termini are both translocated, termed (NC)E3-6.7K). Due to the translocation of a positively charged domain, both the (Ctm)E3-6.7K and (NC)E3-6.7K topologies of E3-6.7K constitute exceptions to the “positive inside” rule. The (Ntm)E3-6.7K and (NC)E3-6.7K are the first examples of posttranslationally translocated proteins in higher eukaryotes that are not tail anchored. Distinct topological forms were also found in transfected cells, as both N and C termini of E3-6.7K were detected on the extracellular surface of transfected cells. The demonstration of unexpected topological forms and translocation mechanisms for E3-6.7K defies conventional thinking about membrane protein topogenesis and advises that both the mode of targeting and topology of signal-anchor proteins should be determined experimentally