Re: How to differentiate plasma membrane vs. cytoplasm in Jurkat lymphocytes?

Posted by Mike Ignatius-3 on
URL: http://confocal-microscopy-list.275.s1.nabble.com/How-to-differentiate-plasma-membrane-vs-cytoplasm-in-Jurkat-lymphocytes-tp7586566p7586581.html

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I worked in lab at UCSF that tried to do LM based assignment of a membrane
associated protein.  They published that it was external and a much sought
after ECM receptor.  Turned out it was internal and the retraction was
forthcoming and quite embarrassing.   Many other examples of this.  IMHO it
takes EM to definitively make that assignment.



On Mon, Mar 6, 2017 at 1:26 PM, Artem Pliss <[hidden email]> wrote:

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> The cytosolic  fraction of a protein can be differentiated from the
> membrane fraction by FLIM. Membrane-bound fluorophore will have a shorter
> lifetime; this is based on difference between refractive indices of cytosol
> and plasma membrane.  See for reference "Refractive index sensing of green
> fluorescent proteins in living cells using fluorescence lifetime imaging
> microscopy" Biophysical Journal (2008), 94 (8), L67-L69
> Best regards
>
> On Mon, Mar 6, 2017 at 3:31 PM, Feinstein, Timothy N <[hidden email]>
> wrote:
>
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> > If you have to work with fixed cells, TIRF might be a good way to go.
> > Cytosolic proteins would get brighter as you adjust the TIRF angle from
> > more stringency to less while PM proteins would not.  If you are working
> > with live cells, FRAP or FLIP would tell you whether they diffuse like
> > membrane-bound proteins or soluble proteins.  Membrane mobility would go
> > down significantly if you decrease the temperature a little.
> >
> > Tim
> >
> > Timothy Feinstein, Ph.D.
> > Research Scientist
> > University of Pittsburgh Department of Developmental Biology
> >
> >
> > On 3/6/17, 2:47 PM, "Confocal Microscopy List on behalf of Swayne,
> Theresa
> > C." <[hidden email] on behalf of
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> >
> >     Dear fellow confocalists,
> >
> >     One of my users would like to determine whether an epitope-tagged
> > protein, expressed in Jurkat cells, is localized to the plasma membrane
> or
> > the cytosol. These cells have only a thin layer of cytoplasm between the
> > nucleus and PM.
> >
> >     It seems to me that at minimum we need a good plasma membrane marker,
> > and control proteins known to be in cytosol and plasma membrane
> > respectively.  Then I’m thinking we could do scanning confocal with high
> NA
> > lens, and profile analysis or overlap analysis to measure the degree of
> > coincidence between the membrane marker and the tagged protein.   Does
> that
> > make sense as a strategy?
> >
> >     If so, do folks have a preferred membrane marker for this cell type?
> > I’ve seen things like CellMask and PKH26, but the images I’ve seen online
> > and in other cell types don’t show “pure” plasma membrane labeling.
> >
> >     Thanks in advance for any suggestions.
> >
> >
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> --
> Artem Pliss
> Research Assistant Professor
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