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closeAre TORC2 and TORC3 also required for long-term potentiation?
Posted by dyjin on 21 Dec 2006 at 12:24 GMT
This interesting paper makes a point on the relevance of TORC1 to L-LTP in the hippocampus and paves the way for further study of the roles of TORCs in the brain, whereby they are abundantly expressed. Importantly, this work provides the first evidence that nuclear accumulation of TORC1 rather than phosphorylation of CREB is critical to L-LTP.
In Figures 1 and S1, it was shown that only TORC1 is expressed in the hippocampus. I would like to make the following comments on this issue:
1) Based on Affymetrix data, a previous work (Conkright et al., Mol. Cell 12:413-423, 2003) has shown that all three TORCs are expressed in hippocampus or temporal lobe (see Figure S2 in that paper).
2) The specificity of anti-TORC1 and anti-TORC2 antibodies used in this study is not known. Based on M&M, it appears that the anti-TORC1 reacts with both TORC1 and TORC3. Does it also bind to TORC2? How about the specificity of anti-TORC2? Are these antibodies isoform-specific?
3) Because TORC1/2/3 are equally active in activating CREB or Tax (Conkright et al., 2003; Iourgenko et al. PNAS 100:12147-12152, 2003; Koga et al., JBC 279:52978-52983, 2004; Siu et al., J. Virol. 80:7052-7059, 2006). It will be very helpful if a more prudent analysis of the roles of TORC2 and TORC3 in L-LTP is performed.
RE: Are TORC2 and TORC3 also required for long-term potentiation?
yzhou replied to dyjin on 22 Dec 2006 at 14:17 GMT
Thank you for your thoughtful comments.
In agree with previous work, we found that both TORCs 1 and 2 were expressed in the
hippocampus, and TORC1 were particularly abundant. However, the mRNA of TORC3 was
undetectable in adult rat hippocampus by RT-PCR, in situ hybridization, and Northern
blot under our conditions.
Our anti-TORC1 antibody recognizes both TORC1 and TORC3 but not TORC2. TORC2
antibody reacts with TORC2 only.
We could not completely exclude the possible role of TORC2 and TORC3 in L-LTP.
Because TORC3 was undetectable and the level of TORC2 was low in hippocampus (See
Figure S1), we focused on TORC1 in this study.