ABSTRACT
As the basic physiological function of synapses, vesicle cycling involves in many aspects of process. Among them, vesicle recycling is the basis of synaptic vesicle cycling. Studies show that clathrin mediated endocytosis is a major pathway of vesicle recycling, in which Dynamin plays an important role. Dynamin is a GTPases with molecular weight of 100 kD, which acts as "scissors" in the endocytosis, separating the clathrin coated pits from membrane. It has been found that Dynamin is associated with epilepsy, Alzheimer's disease, centronuclear myopathy, and several other neurological diseases. In this paper, we discussed the structure, function and regulation of Dynamin, and reviewed recent advance in the studies on Dynamin related diseases.
Subject(s)
Humans , Clathrin , Physiology , Coated Pits, Cell-Membrane , Physiology , Dynamins , Physiology , Endocytosis , Synapses , Physiology , Synaptic Transmission , Synaptic Vesicles , PhysiologyABSTRACT
The most efficient means of protein internalization from the membrane are through clathrin-coated pits, which concentrate protein interactions with the clathrin-associated assembly protein complex AP-2 and internalization signals in the cytoplasmic domain of transmembrane proteins. Binding of clathrin assembly protein to clathrin triskelia induces their assembly into clathrin-coated vesicles (CCVs). Due to a difficulty of isolating clathrin molecules from their complex or assembly state in the cells, most of the studies were carried out with recombinant clathrin proteins, which may present different conformation and structural variation. In this study, we have developed an efficient method of isolating the native clathrin assembly protein lymphoid myeloid (CALM) from the bovine brain that is enriched with clathrin and clathrin associated proteins and characterized by their sensitivity to proteases and it's ability to form CCV. The purified CALM has molecular weight of approximately 100,000 dalton on SDS-PAGE, which is consistent with the result of in vitro translation. The purified CALM protein could promote the assembly of clathrin triskelia into clathrin cage, and cleaved CALM proteolysed by caspase 3 and calpain could not promote them. In this respect, our data support a model in which CALM functions like AP180 as a monomeric clathrin assembly protein and might take part in apoptotic process in neuronal cells.
Subject(s)
Cattle , Adaptor Proteins, Vesicular Transport , Animals , Brain Chemistry , Calpain/metabolism , Carrier Proteins , Caspases/metabolism , Clathrin/metabolism , Coated Pits, Cell-Membrane/metabolism , Hydrolysis , Membrane Proteins , Molecular Weight , Nerve Tissue Proteins/chemistry , Neurons/chemistry , Protein Binding , Protein Conformation , Recombinant Proteins/chemistryABSTRACT
The most efficient means of protein internalization from the membrane are through clathrin-coated pits, which concentrate protein interactions with the clathrin-associated assembly protein complex AP-2 and internalization signals in the cytoplasmic domain of transmembrane proteins. Binding of clathrin assembly protein to clathrin triskelia induces their assembly into clathrin-coated vesicles (CCVs). Due to a difficulty of isolating clathrin molecules from their complex or assembly state in the cells, most of the studies were carried out with recombinant clathrin proteins, which may present different conformation and structural variation. In this study, we have developed an efficient method of isolating the native clathrin assembly protein lymphoid myeloid (CALM) from the bovine brain that is enriched with clathrin and clathrin associated proteins and characterized by their sensitivity to proteases and it's ability to form CCV. The purified CALM has molecular weight of approximately 100,000 dalton on SDS-PAGE, which is consistent with the result of in vitro translation. The purified CALM protein could promote the assembly of clathrin triskelia into clathrin cage, and cleaved CALM proteolysed by caspase 3 and calpain could not promote them. In this respect, our data support a model in which CALM functions like AP180 as a monomeric clathrin assembly protein and might take part in apoptotic process in neuronal cells.
Subject(s)
Cattle , Adaptor Proteins, Vesicular Transport , Animals , Brain Chemistry , Calpain/metabolism , Carrier Proteins , Caspases/metabolism , Clathrin/metabolism , Coated Pits, Cell-Membrane/metabolism , Hydrolysis , Membrane Proteins , Molecular Weight , Nerve Tissue Proteins/chemistry , Neurons/chemistry , Protein Binding , Protein Conformation , Recombinant Proteins/chemistryABSTRACT
Amiloride (AM) is a well known potassium sparing diuretic. The effects of AM at the cellular level include blockade of Na+/H+ exchange in several tissues and inhibition of passive sodium flux in epithelial cells. In this study we have explored the interactions of amiloride with muscarinic receptors, using isolated rat tracheal rings and compared its effects to those of the muscarinic receptor subtype-selective antagonist pirenzepine (PZ). The results obtained demonstrate the ability of AM (100 uM to 1mM) to inhibit the ACh induced rat tracheall contractions. The inhibition resulted in the reduction of the Emax values of ACh in this preparation, and the apparent Ki for AM was of 478 uM. This effect was also observed in a sodium-free choline medium, indicating that it is independent from sodium transport mechanisms sensitive to AM. In contrast to AM, PZ displayed a surmountable type of antagonism with a pA2 value of 6.52. The results demonstrate a differential antagonism by AM and PZ of the muscarinic receptors present in the smooth muscle of the rat trachea