SOCS-3 a better marker of activation and inhibition by leptin than c-Fos?

The one (one of a few) disadvantage of c-Fos as a marker of recent neuronal activity is that it only shows neurons activated by a certain response in question and not those inhibited by the said response.

One solution -- at least in terms of neuronal activation in response to leptin -- could be SOCS-3.

SOCS-3
- is a suppressor of cytokine signaling-3
- ''an intracellular protein induced by activation of cytokine receptors such as the leptin signaling by blocking phosphorylation of the receptor and downstream STAT proteins involved in leptin receptor-activated signal transduction [45,46].'' (Baskin et al., 2000)
- ''In CHO cells transfected with ObRb, expression of SOCS-3 inhibits leptin-induced tyrosine phosphorylation of JAK2 proteins, suggesting that SOCS-3 is a leptin-regulated inhibitor of proximal leptin signaling in vivo [47].'' (Baskin et al., 2000)

So if we use c-Fos as a marker of a response to leptin, only neurons that are activated by leptin (such as ARC POMC neurons) will be shown (Elias et al., 1999). But is we use SOCS-3 as a marker of a response to leptin, we could identify neurons that are activated by leptin (ARC POMC neurons) AND those that are inhibited by leptin (such as ARC NPY/AgRP neurons) (Elias et al., 1999).


references:
- Baskin DG et al. (2000). SOCS-3 expression in leptin-sensitive neurons of the hypothalamus of fed and fasted rats. Regulatory Peptides;92:9-15.
- Elias CF, Aschkenasi C, Lee C, Kelly J, Ahima RS, Bjorbaek C et al. (1999). Leptin differentially regulates NPY and POMC neurons projecting to the lateral hypothalamic area. Neuron;23:775–86.