Journal Watch: MHC and intracellular self

FORSDYKE at QUCDN.QueensU.CA FORSDYKE at QUCDN.QueensU.CA
Tue Aug 18 15:16:18 EST 1992


In article <1992Aug18.013306.4745 at news2.cis.umn.edu>, shiv at tsp.med.umn.edu (Shiv
Prasad) says:
>
>In article <92230.175700FORSDYKE at QUCDN.QueensU.CA> <FORSDYKE at QUCDN.QueensU.CA>
>writes:
>
>>  Start, by forgetting about cells and imagine placing a set of "self"
>>cytosolic proteins in a test tube (A,B,C,D,E,F,G,H). Now add a not-self
>>protein (X). The problem is to find a way of specifically selecting X for
>>degradation. Double the concentration of all the proteins. Nothing
>>happens. Double again, and again. Something is now happening. One of the
>>proteins is aggregating. It is doing this specifically, self with self.
>>The mechanism for this is set out in Lauffer's book "Entropy-driven
>>Processes in Biology (Springer. 1975). Now, as we have it set up,
>>there is no particular reason for any one protein to be the first to
>>aggregate. It could be one of A to H. It could be X. But once it has
>>aggregated, it has marked itself as different. As such, it might be
>>recognized by a specific proteolytic complex (proteosome?) and some of
>>its peptides made available for coupling to MHC protein.

  Prasad replies:

>In your experiment it would seem that whichever protein aggregates first
>would depend on the initial concentration of each protein, and the homotypic
>affinities.  A situatioon in which the non-self would be in excess (to move

   Yes. So, what determines the concentration of self proteins in a cell?

>this back into the cell) is a viral infection, where certain viral proteins
>are made far in excess of the cellular proteins.  If the viral proteins are

  Yes. So what determines the concentration of viral proteins in a cell?

>Going back to the cell-free scenario (i.e. this just popped into my mind)
>the viral proteins may be in excess of the cellular proteins, and they may
>also aggregate more easily, since an aggregate of one protein often forms
>a viral capsid.  So I can see there where X would aggregate before A-H.

 Under what conditions would the virus be in "excess"?

          Sincerely,
          Don Forsdyke

References:   Forsdyke, D. (1992) Bionet.immunology 812 947edt
              Prasad, S. (1992) Bionet.immunology 814 1516gmt
              Forsdyke, D. (1992) Bionet.immunology 817 1757edt
              Prasad, S. (1992) Bionet.immunology 818 133gmt



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