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. 1977 Jul 1;74(1):204–225. doi: 10.1083/jcb.74.1.204

The structure of postsynaptic densities isolated from dog cerebral cortex: II. characterization and arrangement of some of the major proteins within the structure

F Blomberg, RS Cohen, P Siekevitz
PMCID: PMC2109869  PMID: 406264

Abstract

An attempt was made to identify some of the proteins of the postsynaptic density (PSD) fraction isolated from dog cerebral cortex. The major protein has been tentatively labeled "neurofilament" protein, on the basis of its 51,000 mol wt correspondence to a protein found in neurofilament preparations. Other proteins are akin to some dog myofibrillar proteins, on the basis if immunological crossreaction and equal sodium dodecyl sulfate (SDS)-gel electrophoretic mobilities. While a protein similar to dog muscle myosin is not present in the PSD fraction, a major protein present is actin, as evident from reactivity with antiactin serum, from SDS-gel mobility, and from amino acid composition. Only very little tubulin may be present in the PSD fraction, as determined by gel electrophoresis. Various treatments of the PSD fraction were attempted in order to extract some proteins, as revealed by gel electrophoresis, and to observe the structural changes of the PSD fraction residue after extraction of these proteins. The PSD is remarkably resistant to various extraction conditions, with only 4 M guanidine being found to extract most of the proteins, except the 51,000 mol wt protein. Disulfide reducing agents such as dithiothreitol (DTT), blocking agents such as p-chloromercuribenzoate (PCMB) (both in the presence of deoxycholate [DOC]), a Ca++ extractor, ethylene glycol-bis (beta- aminoethyl ether) N,N,N',N'-tetraacetate (EGTA), and guanidine caused an opening up of the native dense PSD structure, revealing approximately 10-nm filaments, presumably consisting of "neurofilament" protein. Both DTT-DOC and PCMB-DOC removed chiefly actin but also some other proteins. EGTA, in greatly opening up the structure, as observed in the electron microscope, revealed both 10-nm and 3- to 5-nm filaments; the later could be composed of actin, since actin was still in the residue after the treatment. EGTA removed a major 18,000 mol wt component and two minor proteins of 68,000 and 73,000 mol wt. Based on the morphological and biochemical evidence, a picture is presented of the PSD as a structure partly made up of 10-nm and 3- to 5-nm filaments, held together through Ca++ interaction and by bonds amendable to breakage by sulfhydrylblocking and disulfide-reducing reagents; either removal of Ca++ and/or rupture of these disulfide bonds opens up the structure. On the basis of the existence of filamentous proteins and the appearance of the PSD after certain treatments as a closed or open structure, a theory is presented with envisages the PSD to function as a modulator in the conduction of the nerve impulse, by movements of its protein relative.

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Selected References

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  1. Blitz A. L., Fine R. E. Muscle-like contractile proteins and tubulin in synaptosomes. Proc Natl Acad Sci U S A. 1974 Nov;71(11):4472–4476. doi: 10.1073/pnas.71.11.4472. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Bloom F. E. The role of cyclic nucleotides in central synaptic function. Rev Physiol Biochem Pharmacol. 1975;74:1–103. doi: 10.1007/3-540-07483-x_19. [DOI] [PubMed] [Google Scholar]
  3. Brekke C. J., Greaser M. L. Separation and characterization of the troponin components from bovine cardiac muscle. J Biol Chem. 1976 Feb 10;251(3):866–871. [PubMed] [Google Scholar]
  4. Cohen R. S., Blomberg F., Berzins K., Siekevitz P. The structure of postsynaptic densities isolated from dog cerebral cortex. I. Overall morphology and protein composition. J Cell Biol. 1977 Jul;74(1):181–203. doi: 10.1083/jcb.74.1.181. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Cotman C. W., Banker G., Churchill L., Taylor D. Isolation of postsynaptic densities from rat brain. J Cell Biol. 1974 Nov;63(2 Pt 1):441–455. doi: 10.1083/jcb.63.2.441. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Cotman C. W., Taylor D. Isolation and structural studies on synaptic complexes from rat brain. J Cell Biol. 1972 Dec;55(3):696–711. doi: 10.1083/jcb.55.3.696. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Dahl D., Bignami A. Glial fibrillary acidic protein from normal and gliosed human brain. Demonstration of multiple related polypeptides. Biochim Biophys Acta. 1975 Mar 28;386(1):41–51. doi: 10.1016/0005-2795(75)90244-5. [DOI] [PubMed] [Google Scholar]
  8. Feit H., Barondes S. H. Colchicine-binding activity in particulate fractions of mouse brain. J Neurochem. 1970 Sep;17(9):1355–1364. doi: 10.1111/j.1471-4159.1970.tb06870.x. [DOI] [PubMed] [Google Scholar]
  9. Fine R. E., Blitz A. L., Hitchcock S. E., Kaminer B. Tropomyosin in brain and growing neurones. Nat New Biol. 1973 Oct 10;245(145):182–186. doi: 10.1038/newbio245182a0. [DOI] [PubMed] [Google Scholar]
  10. Fine R. E., Bray D. Actin in growing nerve cells. Nat New Biol. 1971 Nov 24;234(47):115–118. doi: 10.1038/newbio234115a0. [DOI] [PubMed] [Google Scholar]
  11. Fine R., Lehman W., Head J., Blitz A. Troponin C in brain. Nature. 1975 Nov 20;258(5532):260–267. doi: 10.1038/258260a0. [DOI] [PubMed] [Google Scholar]
  12. Gergely J. Excitation-contraction coupling--cardiac muscle events in the myofilament. Fed Proc. 1976 May 1;35(6):1283–1287. [PubMed] [Google Scholar]
  13. Gray E. G., Guillery R. W. Synaptic morphology in the normal and degenerating nervous system. Int Rev Cytol. 1966;19:111–182. doi: 10.1016/s0074-7696(08)60566-5. [DOI] [PubMed] [Google Scholar]
  14. Gray E. G. Synaptic fine structure and nuclear, cytoplasmic and extracellular networks: The stereoframework concept. J Neurocytol. 1975 Jun;4(3):315–339. doi: 10.1007/BF01102116. [DOI] [PubMed] [Google Scholar]
  15. Greaser M. L., Gergely J. Purification and properties of the components from troponin. J Biol Chem. 1973 Mar 25;248(6):2125–2133. [PubMed] [Google Scholar]
  16. Gruenstein E., Rich A. Non-identity of muscle and non-muscle actins. Biochem Biophys Res Commun. 1975 May 19;64(2):472–477. doi: 10.1016/0006-291x(75)90345-9. [DOI] [PubMed] [Google Scholar]
  17. Gurd J. W. Synaptic plasma membrane glycoproteins: molecular identification of lectin receptors. Biochemistry. 1977 Feb 8;16(3):369–374. doi: 10.1021/bi00622a005. [DOI] [PubMed] [Google Scholar]
  18. HODGKIN A. L. Ionic movements and electrical activity in giant nerve fibres. Proc R Soc Lond B Biol Sci. 1958 Jan 1;148(930):1–37. doi: 10.1098/rspb.1958.0001. [DOI] [PubMed] [Google Scholar]
  19. Hansson H. A., Hydén H. A membrane-associated network of protein filaments in nerve cells. Neurobiology. 1974;4(6):364–375. [PubMed] [Google Scholar]
  20. Iqbal K., Wiśniewski H. M., Shelanski M. L., Brostoff S., Liwnicz B. H., Terry R. D. Protein changes in senile dementia. Brain Res. 1974 Sep 6;77(2):337–343. doi: 10.1016/0006-8993(74)90798-7. [DOI] [PubMed] [Google Scholar]
  21. Johnson L. S., Sinex F. M. On the relationship of brain filaments to microtubules. J Neurochem. 1974 Mar;22(3):321–326. doi: 10.1111/j.1471-4159.1974.tb07594.x. [DOI] [PubMed] [Google Scholar]
  22. Jones D. G., Brearley R. F. Further studies on synaptic junctions. II. A comparison of synaptic ultrastructure in fractionated and intact cerebral cortex. Z Zellforsch Mikrosk Anat. 1972;125(4):432–447. [PubMed] [Google Scholar]
  23. Kelly P. T., Cotman C. W. Identification of glycoproteins and proteins at synapses in the central nervous system. J Biol Chem. 1977 Jan 25;252(2):786–793. [PubMed] [Google Scholar]
  24. Kelly P. T., Cotman C. W. Intermolecular disulfide bonds at central nervous system synaptic junctions. Biochem Biophys Res Commun. 1976 Dec 20;73(4):858–864. doi: 10.1016/0006-291x(76)90200-x. [DOI] [PubMed] [Google Scholar]
  25. Kornguth S. E., Sunderland E. Isolation and partial characterization of a tubulin-like protein from human and swine synaptosomal membranes. Biochim Biophys Acta. 1975 May 30;393(1):100–114. doi: 10.1016/0005-2795(75)90220-2. [DOI] [PubMed] [Google Scholar]
  26. Le Beux Y. J. An ultrastructural study of the synaptic densities, nematosomes, neurotubules, neurofilaments and of a further three-dimensional filamentous network as disclosed by the E-PTA staining procedure. Z Zellforsch Mikrosk Anat. 1973;143(2):239–272. doi: 10.1007/BF00307481. [DOI] [PubMed] [Google Scholar]
  27. Masaki T., Takaiti O., Ebashi S. "M-substance", a new protein constituting the M-line of myofibrils. J Biochem. 1968 Dec;64(6):909–910. doi: 10.1093/oxfordjournals.jbchem.a128975. [DOI] [PubMed] [Google Scholar]
  28. Matus A. I., Walters B. B., Jones D. H. Junctional ultrastructure in isolated synaptic membranes. J Neurocytol. 1975 Jun;4(3):357–367. doi: 10.1007/BF01102118. [DOI] [PubMed] [Google Scholar]
  29. Matus A. I., Walters B. B., Mughal S. Immunohistochemical demonstration of tubulin associated with microtubules and synaptic junctions in mammalian brain. J Neurocytol. 1975 Dec;4(6):733–744. doi: 10.1007/BF01181633. [DOI] [PubMed] [Google Scholar]
  30. Matus A. I., Walters B. B. Ultrastructure of the synaptic junctional lattice isolated from mammalian brain. J Neurocytol. 1975 Jun;4(3):369–375. doi: 10.1007/BF01102119. [DOI] [PubMed] [Google Scholar]
  31. Millward G. R., Woods E. F. Crystals of tropomyosin from various sources. J Mol Biol. 1970 Sep 28;52(3):585–588. doi: 10.1016/0022-2836(70)90421-3. [DOI] [PubMed] [Google Scholar]
  32. Moring S., Ruscha M., Cooke P., Samson F. Isolation and polymerization of brain actin. J Neurobiol. 1975 Mar;6(2):245–255. doi: 10.1002/neu.480060210. [DOI] [PubMed] [Google Scholar]
  33. Olsen R. W. Filamentous protein model for cyclic AMP-mediated cell regulatory mechanisms. J Theor Biol. 1975 Feb;49(2):263–287. doi: 10.1016/0022-5193(75)90172-1. [DOI] [PubMed] [Google Scholar]
  34. PERRY S. V., ZYDOWO M. The nature of the extra protein fraction from myofibrils of striated muscle. Biochem J. 1959 Feb;71(2):220–228. doi: 10.1042/bj0710220. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Peters A., Kaiserman-Abramof I. R. The small pyramidal neuron of the rat cerebral cortex. The synapses upon dendritic spines. Z Zellforsch Mikrosk Anat. 1969 Sep 22;100(4):487–506. doi: 10.1007/BF00344370. [DOI] [PubMed] [Google Scholar]
  36. Pollard T. D., Weihing R. R. Actin and myosin and cell movement. CRC Crit Rev Biochem. 1974 Jan;2(1):1–65. doi: 10.3109/10409237409105443. [DOI] [PubMed] [Google Scholar]
  37. Puszkin S., Berl S. Actomyosin-like protein from brain. Separation and characterization of the actin-like component. Biochim Biophys Acta. 1972 Mar 16;256(3):695–709. doi: 10.1016/0005-2728(72)90204-6. [DOI] [PubMed] [Google Scholar]
  38. Rees M. K., Young M. Studies on the isolation and molecular properties of homogeneous globular actin. Evidence for a single polypeptide chain structure. J Biol Chem. 1967 Oct 10;242(19):4449–4458. [PubMed] [Google Scholar]
  39. Roy R. K., Potter J. D., Sarkar S. Characterization of the Ca2+-regulatory complex of chick embryonic muscles: polymorphism of tropomyosin in adult and embryonic fibers. Biochem Biophys Res Commun. 1976 May 3;70(1):28–36. doi: 10.1016/0006-291x(76)91104-9. [DOI] [PubMed] [Google Scholar]
  40. Shelanski M. L., Albert S., DeVries G. H., Norton W. T. Isolation of filaments from brain. Science. 1971 Dec 17;174(4015):1242–1245. doi: 10.1126/science.174.4015.1242. [DOI] [PubMed] [Google Scholar]
  41. Therien H. M., Mushynski W. E. Isolation of synaptic junctional complexes of high structural integrity from rat brain. J Cell Biol. 1976 Dec;71(3):807–822. doi: 10.1083/jcb.71.3.807. [DOI] [PMC free article] [PubMed] [Google Scholar]
  42. Walters B. B., Matus A. I. Tubulin in postynaptic junctional lattice. Nature. 1975 Oct 9;257(5526):496–498. doi: 10.1038/257496a0. [DOI] [PubMed] [Google Scholar]
  43. Watterson D. M., Harrelson W. G., Jr, Keller P. M., Sharief F., Vanaman T. C. Structural similarities between the Ca2+-dependent regulatory proteins of 3':5'-cyclic nucleotide phosphodiesterase and actomyosin ATPase. J Biol Chem. 1976 Aug 10;251(15):4501–4513. [PubMed] [Google Scholar]

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