Membrane (Contact) Digestion

1965 ◽  
Vol 45 (3) ◽  
pp. 555-595 ◽  
Author(s):  
A. M. Ugolev
Keyword(s):  
Contact Digestion ◽  
Membrane Contact

Some interface phenomena in parasitic protozoa and platyhelminths

1973 ◽  
Vol 51 (3) ◽  
pp. 367-377 ◽  
Author(s):  
J. D. Smyth
Keyword(s):  
Molecular Mimicry ◽  
Intimate Contact ◽  
Interface Phenomena ◽  
Contact Digestion ◽  
Membrane Contact ◽  
Membrane Type ◽  
Host Parasite ◽  
Type 3

The host–parasite interface is defined broadly as a region of intimate contact between host and parasite surfaces. The limitations of this definition are considered. The difficulties of studying the morphology, ultrastructure, and physiology of this region are discussed. Possible host–parasite interfaces appear to fall (theoretically) into one of the following categories: type 1: membrane-to-membrane; type 2A: cytoplasm-to-membrane; type 2B: membrane-to-cytoplasm; type 3: cytoplasm-to-cytoplasm. Phenomena associated with the interface region are various forms of membrane transport, pinocytosis, excretion, secretion, and membrane (= contact) digestion. The apparent role of the interface in differentiation in the protozoan Gregarina polymorpha and the cestode Echinococcus granulosus are discussed. The immunological significance of intimate contact between host and parasite and the various hypotheses to account for the (apparent) 'molecular mimicry' by the parasite, of host surface antigens, are briefly summarized.

Membrane (contact) digestion in the three species of tapeworm Hymenolepis diminuta, Hymenolepis microstoma and Moniezia expansa

Parasitology ◽  
1968 ◽  
Vol 58 (3) ◽  
pp. 535-546 ◽  
Author(s):  
E. W. Taylor ◽  
J. N. Thomas
Keyword(s):  
Electron Microscope ◽  
Hymenolepis Diminuta ◽  
Contact Digestion ◽  
Rate Of Hydrolysis ◽  
Membrane Contact ◽  
Rats And Mice ◽  
Meat Market ◽  
Hydrolysis Of ◽  
Hymenolepis Microstoma

The presence of living tapeworm increases the rate of hydrolysis of starch by α-amylase in vitro. This effect indicates that ‘membrane digestion’ may be one function of the tegument of tapeworms. The effect varies with the surface area and region of the tapeworm. Fixed tapeworm pieces do not enhance starch hydrolysis. The results may provide evidence both for and against the current explanations of membrane digestion. Some possible mechanisms involved in membrane digestion in tapeworms are considered. The importance of membrane digestion in the physiology of gut parasites and the possibility of its wide occurrence are discussed.We wish to thank Dr J. Llewellyn for his criticism and advice during the preparation of this manuscript and for providing rats and mice infected with Hymenolepis. We also thank Dr R. A. Thornhill for examining some tapeworm tissue under the electron microscope; also Mr A. Wilson of the Meat Inspection Department of the Birmingham Meat Market for his unfailing co-operation.

Superficial or Membrane Digestion of Peptides in Dinitrophenol-Inhibited Rat Small Intestine

1979 ◽  
Vol 57 (2) ◽  
pp. 217-220 ◽  
Author(s):  
M. L. G. Gardner
Keyword(s):  
Amino Acids ◽  
Small Intestine ◽  
Free Amino ◽  
Rat Small Intestine ◽  
Peptide Hydrolysis ◽  
Brush Border Enzymes ◽  
Contact Digestion ◽  
Membrane Contact ◽  
Hydrolysis Of ◽  
Important Site

1. Hydrolysis of peptides has been measured in isolated rat small intestine perfused with a pancreatic digest of lactalbumin in the presence of 2,4-dinitrophenol. 2. Although transport of water and amino acids was severely inhibited by 2,4-dinitrophenol, peptide hydrolysis to free amino acids was apparently unimpaired. 3. Only a small fraction of the hydrolysis observed could be accounted for by leakage of enzymes into the lumen. 4. The results show that the brush-border enzymes proximal to the transport mechanism(s) can be an important site of hydrolysis of peptides to amino acids under conditions where the transport of unhydrolysed peptides is inhibited. The results are consistent with the concept of membrane (contact) digestion, although the significance of intracellular hydrolysis and of transmural transport of intact peptides is also discussed.

scholarly journals Annexin A6 modulates TBC1D15/Rab7/StARD3 axis to control endosomal cholesterol export in NPC1 cells

2019 ◽  
Vol 77 (14) ◽  
pp. 2839-2857 ◽  
Author(s):  
Elsa Meneses-Salas ◽  
Ana García-Melero ◽  
Kristiina Kanerva ◽  
Patricia Blanco-Muñoz ◽  
Frederic Morales-Paytuvi ◽  
...  
Keyword(s):  
Late Endosome ◽  
Dependent Manner ◽  
Lipid Transfer ◽  
Cholesterol Accumulation ◽  
Membrane Contact Sites ◽  
Late Endosomes ◽  
Membrane Contact ◽  
Domain 3 ◽  
Niemann Pick ◽  
Mutant Cells

Abstract Cholesterol accumulation in late endosomes is a prevailing phenotype of Niemann-Pick type C1 (NPC1) mutant cells. Likewise, annexin A6 (AnxA6) overexpression induces a phenotype reminiscent of NPC1 mutant cells. Here, we demonstrate that this cellular cholesterol imbalance is due to AnxA6 promoting Rab7 inactivation via TBC1D15, a Rab7-GAP. In NPC1 mutant cells, AnxA6 depletion and eventual Rab7 activation was associated with peripheral distribution and increased mobility of late endosomes. This was accompanied by an enhanced lipid accumulation in lipid droplets in an acyl-CoA:cholesterol acyltransferase (ACAT)-dependent manner. Moreover, in AnxA6-deficient NPC1 mutant cells, Rab7-mediated rescue of late endosome-cholesterol export required the StAR-related lipid transfer domain-3 (StARD3) protein. Electron microscopy revealed a significant increase of membrane contact sites (MCS) between late endosomes and ER in NPC1 mutant cells lacking AnxA6, suggesting late endosome-cholesterol transfer to the ER via Rab7 and StARD3-dependent MCS formation. This study identifies AnxA6 as a novel gatekeeper that controls cellular distribution of late endosome-cholesterol via regulation of a Rab7-GAP and MCS formation.

scholarly journals Caenorhabditis elegans Junctophilin has tissue-specific functions and regulates neurotransmission with extended-synaptotagmin

Genetics ◽  
2021 ◽  
Author(s):  
Christopher A Piggott ◽  
Zilu Wu ◽  
Stephen Nurrish ◽  
Suhong Xu ◽  
Joshua M Kaplan ◽  
...  
Keyword(s):  
Calcium Channels ◽  
Calcium Channel ◽  
Tissue Specific ◽  
Voltage Gated ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Pharyngeal Muscles ◽  
Membrane Contact ◽  
Null Mutants

Abstract The junctophilin family of proteins tether together plasma membrane (PM) and endoplasmic reticulum (ER) membranes, and couple PM- and ER-localized calcium channels. Understanding in vivo functions of junctophilins is of great interest for dissecting the physiological roles of ER-PM contact sites. Here, we show that the sole C. elegans junctophilin JPH-1 localizes to discrete membrane contact sites in neurons and muscles and has important tissue-specific functions. jph-1 null mutants display slow growth and development due to weaker contraction of pharyngeal muscles, leading to reduced feeding. In the body wall muscle, JPH-1 co-localizes with the PM-localized EGL-19 voltage-gated calcium channel and ER-localized UNC-68/RyR calcium channel, and is required for animal movement. In neurons, JPH-1 co-localizes with the membrane contact site protein Extended-SYnaptoTagmin 2 (ESYT-2) in soma, and is present near presynaptic release sites. Interestingly, jph-1 and esyt-2 null mutants display mutual suppression in their response to aldicarb, suggesting that JPH-1 and ESYT-2 have antagonistic roles in neuromuscular synaptic transmission. Additionally, we find an unexpected cell non-autonomous effect of jph-1 in axon regrowth after injury. Genetic double mutant analysis suggests that jph-1 functions in overlapping pathways with two PM-localized voltage-gated calcium channels, egl-19 and unc-2, and unc-68/RyR for animal health and development. Finally, we show that jph-1 regulates the colocalization of EGL-19 and UNC-68 and that unc-68/RyR is required for JPH-1 localization to ER-PM puncta. Our data demonstrate important roles for junctophilin in cellular physiology, and also provide insights into how junctophilin functions together with other calcium channels in vivo.

scholarly journals Remodelling of Nucleus-Vacuole Junctions During Metabolic and Proteostatic Stress

Contact ◽  
2021 ◽  
Vol 4 ◽  
pp. 251525642110166
Author(s):  
Verena Kohler ◽  
Sabrina Büttner
Keyword(s):  
Nuclear Envelope ◽  
Internal Stress ◽  
Molecular Architecture ◽  
Adaptation To Stress ◽  
Semipermeable Membranes ◽  
Cellular Adaptation ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Intracellular Compartments ◽  
Membrane Contact

Cellular adaptation to stress and metabolic cues requires a coordinated response of different intracellular compartments, separated by semipermeable membranes. One way to facilitate interorganellar communication is via membrane contact sites, physical bridges between opposing organellar membranes formed by an array of tethering machineries. These contact sites are highly dynamic and establish an interconnected organellar network able to quickly respond to external and internal stress by changing size, abundance and molecular architecture. Here, we discuss recent work on nucleus-vacuole junctions, connecting yeast vacuoles with the nucleus. Appearing as small, single foci in mitotic cells, these contacts expand into one enlarged patch upon nutrient exhaustion and entry into quiescence or can be shaped into multiple large foci essential to sustain viability upon proteostatic stress at the nuclear envelope. We highlight the remarkable plasticity and rapid remodelling of these contact sites upon metabolic or proteostatic stress and their emerging importance for cellular fitness.

scholarly journals Synaptotagmins at the endoplasmic reticulum–plasma membrane contact sites maintain diacylglycerol homeostasis during abiotic stress

2021 ◽  
Author(s):  
Noemi Ruiz-Lopez ◽  
Jessica Pérez-Sancho ◽  
Alicia Esteban del Valle ◽  
Richard P Haslam ◽  
Steffen Vanneste ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Abiotic Stress ◽  
Fluorescent Protein ◽  
Mechanical Damage ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
Green Fluorescent

Abstract Endoplasmic reticulum-plasma membrane contact sites (ER-PM CS) play fundamental roles in all eukaryotic cells. Arabidopsis thaliana mutants lacking the ER-PM protein tether synaptotagmin1 (SYT1) exhibit decreased plasma membrane (PM) integrity under multiple abiotic stresses such as freezing, high salt, osmotic stress and mechanical damage. Here, we show that, together with SYT1, the stress-induced SYT3 is an ER-PM tether that also functions in maintaining PM integrity. The ER-PM CS localization of SYT1 and SYT3 is dependent on PM phosphatidylinositol-4-phosphate and is regulated by abiotic stress. Lipidomic analysis revealed that cold stress increased the accumulation of diacylglycerol at the PM in a syt1/3 double mutant relative to wild type while the levels of most glycerolipid species remain unchanged. Additionally, the SYT1-green fluorescent protein (GFP) fusion preferentially binds diacylglycerol in vivo with little affinity for polar glycerolipids. Our work uncovers a SYT-dependent mechanism of stress adaptation counteracting the detrimental accumulation of diacylglycerol at the PM produced during episodes of abiotic stress.

Sign in / Sign up

Export Citation Format

Share Document