Differential recognition of a dileucine-based sorting signal by AP-1 and AP-3 reveals a requirement for both BLOC-1 and AP-3 in delivery of OCA2 to melanosomes

Cell types that generate unique lysosome-related organelles (LROs), such as melanosomes in melanocytes, populate nascent LROs with cargoes that are diverted from endosomes. Cargo sorting toward melanosomes correlates with binding via cytoplasmically exposed sorting signals to either heterotetrameric adaptor AP-1 or AP-3. Some cargoes bind both adaptors, but the relative contribution of each adaptor to cargo recognition and their functional interactions with other effectors during transport to melanosomes are not clear. Here we exploit targeted mutagenesis of the acidic dileucine-based sorting signal in the pigment cell-specific protein OCA2 to dissect the relative roles of AP-1 and AP-3 in transport to melanosomes. We show that binding to AP-1 or AP-3 depends on the primary sequence of the signal and not its position within the cytoplasmic domain. Mutants that preferentially bound either AP-1 or AP-3 each trafficked toward melanosomes and functionally complemented OCA2 deficiency, but AP-3 binding was necessary for steady-state melanosome localization. Unlike tyrosinase, which also engages AP-3 for optimal melanosomal delivery, both AP-1- and AP-3-favoring OCA2 variants required BLOC-1 for melanosomal transport. These data provide evidence for distinct roles of AP-1 and AP-3 in OCA2 transport to melanosomes and indicate that BLOC-1 can cooperate with either adaptor during cargo sorting to LROs.     

On the Inhibitory Affect of Some Dementia Drugs on DNA Polymerase β Activity

Some drugs are routinely prescribed for dementia that sets in either due to normal ageing or due to neurodegenerative disorders. We have studied the effect of three of these drugs, Donepezil hydrochloride, Rivastigmine tartrate and Nootropyl, on the activity of DNA polymerases β, a crucial enzyme in the base excision repair pathway, the most important mode of DNA repair in brain. All the three drugs inhibited DNA polymerase β activity to varying degrees although the affects of Donepezil being the least and inconsistent. The drugs preferentially bind to and inhibit the activities of 8 kDa domain of DNA polymerase β that is known to possess the dRP lyase activity. The function of 31 kDa domain dealing with template driven addition of nucleotides at 3′ end of the primer is not adversely affected. The inhibitory action of most widely used dementia drugs on DNA repair potential signifies that pharma sector needs to consider this aspect especially while designing drugs targeted towards brain. N. S. Chary—On project assignment from J.J College of Arts and Science, Tiruchirapally, Tamilnadu, India-620024.     

Inhibition of Pigments and Phycocolloid in a Marine Red Alga Gracilaria Edulis by Ultraviolet-B Radiation

Vegetative fragments of the subtidal macroalga Gracilaria edulis (Gmel.) Silva cultured under field conditions at Thonithurai were subjected in the laboratory to UV-B radiation (280 – 320 nm). UV-B inhibited the accumulation of chlorophyll and phycobiliproteins, and lowered agar yield (23 to 43%) and its gel strength (22 to 36%) under 12 to 72 h exposure. The longer the exposure to UV-B radiation the more significant impact on pigments and phycocolloid properties of Gracilaria edulis was observed.     

Inhibition of thymidine kinase activity by hydroxyurea during highly and less proliferative regions of rat brain

Hydroxyurea, when injected intraperitoneally, exerted marked inhibition on the activity of thymidine kinase in 5 day old postnatal cerebellum and 15 day old embryonic cerebrum. However, it failed to show any sustained inhibition on thymidine kinase activity in 5 day old postnatal cerebrum. In this case, the marginal decrease of thymidine kinase activity noticed during early intervals reversed back to more than normal value at a later time interval. These results along with our earlier findings are taken to indicate the differential action of this drug on thymidine kinase activity in rapidly and slowly proliferating regions of rat brain     

The effect of gum arabic on infection and nodulation of cluster clover by Rhizobium

Summary Gum arabic is an adhesive used in pelleting legume seeds with Rhizobium. The present study shows that the gum generally enhances the number of infected root hairs, promotes early nodulation and significantly increases the number of leaves during initial nodulation of cluster clover (Trifolium glomeratum) inoculated with Rhizobium trifolii under bacteriologically controlled conditions.     

Computer-aided, rational design of a potent and selective small peptide inhibitor of cyclooxygenase 2 (COX2)

Cyclooxygenase (COX) is a key enzyme in the biosynthetic pathway leading to the formation of prostaglandins, which are the mediators of inflammation. This enzyme exists mainly in two isoforms, COX1 and COX2. Prostaglandins responsible for the inflammatory process could be sufficiently controlled with the conventional non-steroidal anti-inflammatory drugs (NSAIDs). These drugs, however, had adverse gastrointestinal side-effects and, therefore, drugs that selectively inhibit COX2, such as the coxibs, were developed. Recent reports on the harmful cardiovascular and renal side-effects of the conventional NSAIDs as well as the COX2 selective inhibitors valdecoxib and rofecoxib have once again led to the quest for a novel class of COX2 selective inhibitors. Keeping this in mind, we have used the available X-ray crystal structures of the complexes of COX1 and COX2 with the known inhibitors to carry out a structure-based, rational, molecular modeling approach to design a small peptide inhibitor, which is both potent and selective for COX2. Docking studies using SYBYL 6.81 (Tripos, Inc.) and AutoDock 3.0, indicate that the designed peptides inhibit COX2 with potency in the nanomolar range. Furthermore, it is found to be a million-fold selective for COX2 as compared with COX1. Thus, the small peptide inhibitor is a suitable lead compound for the design of a new class of anti-inflammatory drugs.