The gene Aedes aegypti intestinal mucin 1 (AeIMUC1) encodes a putative peritrophic matrix (PM) protein that is expressed in the midgut of mosquito larvae and adults and is upregulated in response to exposure to heavy metals. The AeIMUC1 protein has a predicted secretory signal peptide and three putative chitin-binding domains (CBDs) with an intervening mucin-like domain. Immunofluorescence and immunoelectron microscopy experiments established that AeIMUC1 is a bona fide PM protein, and binding of the recombinant protein to chitin was demonstrated in vitro. Previous experiments suggested that the Ae. aegypti PM can bind toxic heme molecules generated during blood digestion. However, the identity of the binding molecule(s) was unknown. Using of heme-agarose beads and spectrophotometric and microcalorimetric titrations, we show that recombinant AeIMUC1 can bind large amounts of heme in vitro, suggesting for the first time a role for a PM protein in heme detoxification during blood digestion. Binding of heme to AeIMUC1 was accompanied by an altered circular dichroism spectrum indicating a change in protein conformation, consistent with an increase in secondary structure. Heme-binding activity was mapped to the AeIMUC1 CBDs, suggesting that these domains possess dual chitin- and heme-binding activity.
The peritrophic matrix (PM) is an extracellular envelope that lines the digestive tract of most insects. It is thought to play key roles in protecting insects from pathogens and facilitating digestion. Until recently, little information was available on the molecular composition of the PM. This review summarizes recent progress in the study of the PM from hematophagous insects, with emphasis on molecular and physiological aspects. Topics discussed include the presence of chitin and protein diversity in the PM, cloning and characterization of genes encoding PM proteins, PM permeability, and the role of the PM as a barrier for pathogens.
Shao, Li-Rong and F. Edward Dudek. Changes in mIPSCs and sIPSCs after kainate treatment: evidence for loss of inhibitory input to dentate granule cells and possible compensatory responses. J Neurophysiol 94: 952-960, 2005. First published March 16, 2005 doi:10.1152/jn.01342.2004. How inhibition is altered after status epilepticus and the role of inhibition during epileptogenesis remain unsettled issues. The present study examined acute (4 -7 days) and chronic (Ͼ3 mo) changes of GABA A receptor-mediated inhibitory synaptic input to dentate granule cells after kainate-induced status epilepticus. Whole cell patch-clamp techniques were used to record spontaneous and miniature inhibitory postsynaptic currents (sIPSCs and mIPSCs) in the presence of 6,7-dinitroquinoxaline-2,3-dione and DL-2-amino-5-phosphonopentanoic acid to block glutamatergic excitatory synaptic transmission. In both groups, mean sIPSC frequency of dentate granule cells from the saline-and kainate-treated rats was not significantly different. However, mIPSC frequency from the kainate-treated rats of both groups was ϳ30% lower than that of the respective saline controls. The mean amplitude of sIPSCs and mIPSCs from kainate-treated rats was not reduced in either the acute or chronic groups. The mean 10 -90% rise time of IPSCs was not altered in kainate-treated rats, but the decay time constant was slightly longer than in controls, and the charge transfer 4 -7 days after kainate treatment was significantly larger. The similar reduction of mIPSC frequency (i.e., ϳ30%) in the two groups of kainate-treated rats suggests a decreased inhibitory input to dentate granule cells (presumably due to a partial loss of inhibitory interneurons that innervate them) without recovery during epileptogenesis. The lack of effect on sIPSC frequency and the decreased mIPSC frequency in both groups suggests a possible compensatory increase in firing rate of interneurons, which may involve a hypothetical reduction of inhibitory input to the remaining interneurons.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.