Synaptic junctions isolated from cerebellum and forebrain: Comparisons of morphological and molecular properties

Groswald, Douglas E.; Montgomery, Paul R.; Kelly, Paul

doi:10.1016/0006-8993(83)90225-1

Cited by 30 publications

(36 citation statements)

References 46 publications

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“…This PSD preparation also contains a substrate protein (7) and a calmodulin-binding protein (8) in the Mr 60,000 range. Substrate proteins (12) and calmodulinbinding proteins (13,14) of Mr 50,000 and 60,000 have also been observed in PSD and synaptic junction (SJ) preparations isolated from rat forebrain. The SJ Mr 50,000 polypeptide is identical to the mPSDp (11,14).…”

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confidence: 99%

“…Previous results on the distribution of the Mr 50,000 mPSDp (11) in neural and non-neural tissue indicated that this protein was present only in brain and only in those subcellular fractions containing identifiable synaptic junctions or postsynaptic densities. In light of the present findings, together with the observation that the mPSDp binds calmodulin (8,13,14) and the demonstration that approximately half of the calmodulin kinase II activity in rat brain homogenates is soluble (2,21), the distribution of the Mr 50,000 mPSDp in subcellular fractions from rat brain has been reexamined. By using the 1251-labeled calmodulin gel overlay method (8) we have found the mPSDp to be present in cytosolic fractions but in -1/10th the amount (per mg total protein) as that in SJ preparations (data not shown).…”

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confidence: 99%

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Evidence that the major postsynaptic density protein is a component of a Ca2+/calmodulin-dependent protein kinase.

Kelly¹,

McGuinness²,

Greengard³

1984

Proc. Natl. Acad. Sci. U.S.A.

345

145

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Polypeptides of Mr 50,000 and 60,000 in isolated synaptic junctions have been compared to polypeptides of corresponding molecular weight in Ca2+/calmodulin-dependent protein kinase II. The polypeptides of corresponding molecular weight from the two preparations were shown by several criteria to be indistinguishable. These criteria included 12'I-labeled tryptic/chymotryptic peptide patterns, 32P-labeled proteolytic peptide maps, and crossreactivity on immunoblots using polyclonal and monoclonal antibodies. Furthermore, studies examining the phosphorylation of substrate proteins, by the endogenous synaptic junction kinase and by Ca2+/calmodulin-dependent protein kinase II, indicated that the two enzymes have similar substrate specificities. Since the Mr 50,000 polypeptide present in synaptic junctions is known to be the major postsynaptic density protein, the present results indicate that the major postsynaptic density protein is a component of Ca2+/calmodulin-dependent protein kinase II.A number of Ca2+/calmodulin-dependent protein kinases have recently been identified in neuronal tissue (for review, see ref. 1). One of these is a kinase purified from rat brain (2) that phosphorylates synapsin I, a synaptic vesicle-associated neuronal protein (3,4). This kinase, designated Ca2+/calmodulin-dependent protein kinase II (calmodulin kinase II), has recently been purified to near homogeneity (5, 6) and exhibits a major Mr 50,000 polypeptide and a less prominent Mr 60,000 polypeptide when analyzed by NaDodSO4/polyacrylamide gel electrophoresis. These Mr 50,000 and 60,000 polypeptides coelute with the peak of kinase activity through a variety of purification procedures, are themselves phosphorylated in a Ca2+/calmodulin-dependent manner, and are calmodulin-binding proteins (5,6).Grab et al. (7) found a calmodulin-sensitive protein kinase in a postsynaptic density (PSD) preparation isolated from canine cerebral cortex. An endogenous Mr 50,000 polypeptide is both a substrate for this kinase (7) and a calmodulin-binding protein (8). This Mr 50,000 polypeptide is the most abundant PSD protein and has been designated the major PSD protein (mPSDp) (9-11). This PSD preparation also contains a substrate protein (7) and a calmodulin-binding protein (8) in the Mr 60,000 range. Substrate proteins (12) and calmodulinbinding proteins (13,14) of Mr 50,000 and 60,000 have also been observed in PSD and synaptic junction (SJ) preparations isolated from rat forebrain. The SJ Mr 50,000 polypeptide is identical to the mPSDp (11,14). Therefore, either SJ or PSD preparations can be used as a source for the mPSDp.The similarities between the Mr 50,000 and 60,000 polypeptides in calmodulin kinase II and those of corresponding molecular weight in SJ preparations prompted us to examine their possible relationship. A preliminary account of this work has been reported (15). METHODSSubcellular Fractionation. Whole forebrains were used to isolate SJ fractions by the iodonitrotetrazolium violet/Triton X-100 method as described (11). Care was t...

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mentioning

confidence: 99%

mentioning

confidence: 99%

Evidence that the major postsynaptic density protein is a component of a Ca2+/calmodulin-dependent protein kinase.

Kelly¹,

McGuinness²,

Greengard³

1984

Proc. Natl. Acad. Sci. U.S.A.

345

145

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“…The contents of these proteins vary in a wide range in PSD of different synapses. For instance, the content of basic protein in the cerebellar cortex synapses is 5-fold lower that in PSD of cerebral cortical synapses [45].…”

Section: Basic Molecular and Spatial Organization Of The Ssumentioning

confidence: 99%

“…An individual PSD consists approximately of 15 major and 10 minor proteins [23,47]. These proteins are: basic 50 kD protein, actin, tubulin, phosphoprotein I, high-molecular-weight microtubular protein, cAMP-and calmodulin-dependent kinases, adenylate cyclase, phosphodiestemse, and various glycoproteins [33,39,43,45,52,61,64,66,691. The basic protein is probably a subunit of calmodulin-activated protein kinase [20,42,60,61].…”

Section: Basic Molecular and Spatial Organization Of The Ssumentioning

confidence: 99%

“…The basic element of all SSU is a filamentous network associated with the postsynaptic membrane [27,63]. The fibrillary/granular composition of PSD in synapses may considerably differ from one part of the brain to another [43,45]. GenemUy, component a of the PSD consists of filaments 4 nm in diameter and component b of filaments up to 9 nm; the network of these thicker filaments extends to 100 nm into the postsynaptic portion of the synapse and is structurally associated with its cytoskeleton and organelles [27,34,47,62].…”

Section: Basic Molecular and Spatial Organization Of The Ssumentioning

confidence: 99%

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Subsynaptic units as a universal system-forming and regulating factor of brain synapses

Semchenko

Stepanov

1997

Bull Exp Biol Med

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Dense projections and postsynaptic density --specialized structures of the synaptic cytoskeleton --are regarded as a single functional system of subsynaptic units. From this viewpoint, interneuronal relations in health and after brain ischemia are analyzed. It is shown that hyperplasia and recombination of the system of subsynaptic units are the major mechanisms responsible for reorganization of functionally mature interneuronal junctions in the mammalian and human brain. Key Words: synapse; synaptic cytoskeleton; dense projections; postsynaptic densityThe relationship between form and content and between quality and quantity at the level of intemeuronal relations are of particular importance, taking into account the role of synapses in neuronal plasticity and the molecular biochemistry, immunohistochemistry, and electron microscopy data [4,7,16,24,38,41,47,65]. Basic structural components and biochemical composition of virtually all brain synapses have been identified. They include: 1) pre-and postsynaptic membranes with receptors and ionic channels and pumps, 2) synaptic cleft substance providing adhesion, transport, and deactivation of neurotransmitters, 3) intrasynaptic structures: simple (synaptic vesicles) and more complex vesicular (various vacuoles, rimmed vesicles, and multivesicular complexes) and filamentous-granular-vesicular (dendritic spikes), and 4) specific structures of presynaptic (dense projections) and postsynaptic (postsynaptic density) cytoskeleton [3,14,47,63,82]. Although large body of evidence has been collected, the problem of integrating structure(s) of the synapse unsolved [6].The idea that paramembrane structures of the cytoskeleton is a single functional system of subsynaptic units (SSU) that integrates the activity of Department of Histology and Embryology, Medical Academy, Omsk the entire synapse was put forward in the 1970s [1,5]. The search for the system-forming factors and their structural equivalents at the level of interneuronal junctions and new electron microscopic data on the structure of paramembrane zones in syalapses [14,18,22,30,44,70] led to the need of interpreting the contribution of dense projections (DP) and postssamptic densities (PSD) to impulse transmission across synapses [1] in structural and functional terms. It was demonstrated that pre-and postsynaptic structures are structurally and functionally continuous and operate as a single complex [1,5]. Molecular mechanisms by which all synaptic structures are integrated in a system of discrete information transfer between neurons have been elucidated [3,24,27,34,47,63,71,77,82].New information regarding synaptic function and the need for morphological indicators of integrative-triggering activity of the brain motivated our interest into the idea of the SSU in the light of recent findings [7][8][9][10][11]13]. We have formulated a concept of the SSU [7,12] and applied it to the analysis of specific pathological and functional states of the brain [7][8][9][10]75]. According to this concept, a SSU that was created o...

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Calcium/Calmodulin-Dependent Protein Phosphorylation in the Nervous System

McGuinness

Lai

Ouimet

et al. 1985

Calcium in Biological Systems

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Synaptic junctions isolated from cerebellum and forebrain: Comparisons of morphological and molecular properties

Cited by 30 publications

References 46 publications

Evidence that the major postsynaptic density protein is a component of a Ca2+/calmodulin-dependent protein kinase.

Evidence that the major postsynaptic density protein is a component of a Ca2+/calmodulin-dependent protein kinase.

Subsynaptic units as a universal system-forming and regulating factor of brain synapses

Calcium/Calmodulin-Dependent Protein Phosphorylation in the Nervous System

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