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An integral protein of the inner nuclear membrane localizes to the mitotic spindle in mammalian cells
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Södertörn University, Sweden.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Södertörn University, Sweden.ORCID iD: 0000-0003-1476-6675
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2009 (English)In: Journal of Cell Science, ISSN 0021-9533, E-ISSN 1477-9137, Vol. 122, no 12, 2100-2107 p.Article in journal (Refereed) Published
Abstract [en]

Here, we characterize a transmembrane protein of the nuclear envelope that we name spindle-associated membrane protein 1 (Samp1). The protein is conserved in metazoa and fission yeast and is homologous to Net5 in rat and Ima1 in Schizosaccharomyces pombe. We show that, in human cells, the protein is a membrane-spanning polypeptide with an apparent molecular mass of 43 kDa. This is consistent with a predicted polypeptide of 392 amino acids that has five transmembrane segments and its C-terminus exposed to the nucleoplasm. During interphase, Samp1 was specifically distributed in the inner nuclear membrane. Post-transcriptional silencing of Samp1 expression resulted in separation of centrosomes from the nuclear envelope, indicating that it is functionally connected to the cytoskeleton. At the onset of mitosis, most of the protein dispersed out into the ER, as expected. However, during mitosis, a significant fraction of the protein specifically localized to the polar regions of the mitotic spindle. We demonstrate for the first time, in human cells, the existence of a membranous structure overlapping with the mitotic spindle. Interestingly, another integral inner nuclear membrane protein, emerin, was absent from the spindle-associated membranes. Thus, Samp1 defines a specific membrane domain associated with the mitotic spindle.

Place, publisher, year, edition, pages
2009. Vol. 122, no 12, 2100-2107 p.
Keyword [en]
Inner nuclear membrane, Transmembrane proteins, Mitotic spindle, Mitosis, Cancer
National Category
Biological Sciences
URN: urn:nbn:se:su:diva-60074DOI: 10.1242/jcs.047373ISI: 000266634800018OAI: diva2:433014

authorCount :6

Available from: 2011-08-08 Created: 2011-08-08 Last updated: 2015-03-06Bibliographically approved
In thesis
1. The functional organization of nuclear membrane proteins and development of new technology for studies of cell signaling
Open this publication in new window or tab >>The functional organization of nuclear membrane proteins and development of new technology for studies of cell signaling
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The eukaryotic cell is defined by the nucleus, which is delimited by a double membrane structure termed the nuclear envelope (NE). The NE is implicated in a multitude of different processes, for example chromatin organization. During mitosis in higher eukaryotes the nucleus is disassembled to allow the formation of the mitotic spindle, which segregates the duplicated chromosomes between daughter cells. We have characterized a novel transmembrane protein of the inner nuclear membrane. Because of its distribution along spindle microtubule during mitosis, we termed the protein Samp1 (Spindle associated membrane protein 1). Samp1 is the founding member of transmembrane proteins that define a novel membrane domain that we have termed the SE (spindle endomembrane). Furthermore, we have shown that in interphase Samp1 specifically interacts with the centrosome and A-type lamina network proteins. Moreover, Samp1 contains an evolutionary highly conserved N-terminal tail containing two putative zinc fingers.

Recent studies indicate local caspase activity in dendrites or axons during development and in neurodegenerative disorders. Here I present the development of a novel and unique system to monitor protease activity at sub-cellular resolution in live cells. This system relies on a cleavable FRET sensor that is anchored to the cytoskeleton. Using this system we demonstrate local caspase activation of the soma in neuronaly differentiated cells. We also used the anchored FRET sensors to monitor caspase activation after treatment with the Alzheimer’s decease related amyloid-β peptide.

Moreover we have improved a NF-ĸB decoy delivery system. The system consists of a cell penetrating peptide, transportan-10, covalently linked to a peptide nucleic acid sequence that hybridizes with a nonanucleotide sequence in the decoy. We show that this system effectively delivered the decoy and inhibited an inflammatory response in primary rat glial cells.

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University, 2011. 54 p.
National Category
Biochemistry and Molecular Biology Cell Biology
Research subject
urn:nbn:se:su:diva-63559 (URN)978-91-7447-386-5 (ISBN)
Public defence
2011-11-25, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Available from: 2011-11-02 Created: 2011-10-23 Last updated: 2015-03-06Bibliographically approved

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