Microdomains of endoplasmic reticulum within the sarcoplasmic reticulum of skeletal myofibers

Kaakinen, Mika; Papponen, Hinni; Metsikkoe, Kalervo

doi:10.1016/j.yexcr.2007.10.009

Title: Microdomains of endoplasmic reticulum within the sarcoplasmic reticulum of skeletal myofibers

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Abstract

The relationship between the endoplasmic reticulum (ER) and the sarcoplasmic reticulum (SR) of skeletal muscle cells has remained obscure. In this study, we found that ER- and SR-specific membrane proteins exhibited diverse solubility properties when extracted with mild detergents. Accordingly, the major SR-specific protein Ca{sup 2+}-ATPase (SERCA) remained insoluble in Brij 58 and floated in sucrose gradients while typical ER proteins were partially or fully soluble. Sphingomyelinase treatment rendered SERCA soluble in Brij 58. Immunofluorescence staining for resident ER proteins revealed dispersed dots over I bands contrasting the continuous staining pattern of SERCA. Infection of isolated myofibers with enveloped viruses indicated that interfibrillar protein synthesis occurred. Furthermore, we found that GFP-tagged Dad1, able to incorporate into the oligosaccharyltransferase complex, showed the dot-like structures but the fusion protein was also present in membranes over the Z lines. This behaviour mimics that of cargo proteins that accumulated over the Z lines when blocked in the ER. Taken together, the results suggest that resident ER proteins comprised Brij 58-soluble microdomains within the insoluble SR membrane. After synthesis and folding in the ER-microdomains, cargo proteins and non-incorporated GFP-Dad1 diffused into the Z line-flanking compartment which likely represents the ER exit sites.

Authors:

Kaakinen, Mika; Papponen, Hinni ^[1]; Metsikkoe, Kalervo ^[1]

Department of Anatomy and Cell Biology, P.O. Box 5000 (Aapistie 7), FIN-90014 University of Oulu (Finland)

Publication Date:: Tue Jan 15 00:00:00 EST 2008

OSTI Identifier:: 21045926

Resource Type:: Journal Article

Journal Name:: Experimental Cell Research

Additional Journal Information:: Journal Volume: 314; Journal Issue: 2; Other Information: DOI: 10.1016/j.yexcr.2007.10.009; PII: S0014-4827(07)00470-3; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0014-4827

Country of Publication:: United States

Language:: English

Subject:: 60 APPLIED LIFE SCIENCES; BIOSYNTHESIS; CELL MEMBRANES; MEMBRANE PROTEINS; MUSCLES; SACCHAROSE; SARCOPLASMIC RETICULUM; VIRUSES

Citation Formats


                    Kaakinen, Mika, Papponen, Hinni, and Metsikkoe, Kalervo. Microdomains of endoplasmic reticulum within the sarcoplasmic reticulum of skeletal myofibers.  United States: N. p., 2008. 
        Web.  doi:10.1016/j.yexcr.2007.10.009.

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                    Kaakinen, Mika, Papponen, Hinni, & Metsikkoe, Kalervo. Microdomains of endoplasmic reticulum within the sarcoplasmic reticulum of skeletal myofibers.  United States.  https://doi.org/10.1016/j.yexcr.2007.10.009

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                    Kaakinen, Mika, Papponen, Hinni, and Metsikkoe, Kalervo. 2008.  
        "Microdomains of endoplasmic reticulum within the sarcoplasmic reticulum of skeletal myofibers".  United States.  https://doi.org/10.1016/j.yexcr.2007.10.009.

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@article{osti_21045926,

  title        = {Microdomains of endoplasmic reticulum within the sarcoplasmic reticulum of skeletal myofibers},

  author       = {Kaakinen, Mika and Papponen, Hinni and Metsikkoe, Kalervo},

  abstractNote = {The relationship between the endoplasmic reticulum (ER) and the sarcoplasmic reticulum (SR) of skeletal muscle cells has remained obscure. In this study, we found that ER- and SR-specific membrane proteins exhibited diverse solubility properties when extracted with mild detergents. Accordingly, the major SR-specific protein Ca{sup 2+}-ATPase (SERCA) remained insoluble in Brij 58 and floated in sucrose gradients while typical ER proteins were partially or fully soluble. Sphingomyelinase treatment rendered SERCA soluble in Brij 58. Immunofluorescence staining for resident ER proteins revealed dispersed dots over I bands contrasting the continuous staining pattern of SERCA. Infection of isolated myofibers with enveloped viruses indicated that interfibrillar protein synthesis occurred. Furthermore, we found that GFP-tagged Dad1, able to incorporate into the oligosaccharyltransferase complex, showed the dot-like structures but the fusion protein was also present in membranes over the Z lines. This behaviour mimics that of cargo proteins that accumulated over the Z lines when blocked in the ER. Taken together, the results suggest that resident ER proteins comprised Brij 58-soluble microdomains within the insoluble SR membrane. After synthesis and folding in the ER-microdomains, cargo proteins and non-incorporated GFP-Dad1 diffused into the Z line-flanking compartment which likely represents the ER exit sites.},

  doi          = {10.1016/j.yexcr.2007.10.009},

  url          = {https://www.osti.gov/biblio/21045926},
  journal      = {Experimental Cell Research},

  issn         = {0014-4827},

  number       = 2,

  volume       = 314,

  place        = {United States},

  year         = {Tue Jan 15 00:00:00 EST 2008},

  month        = {Tue Jan 15 00:00:00 EST 2008}

}

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