Time- and Polarity-dependent Proteomic Changes associated with Homeostatic Scaling at Central Synapses

In homeostatic scaling, the cellular mechanisms that detect the offset from the set-point, the duration of the offset and implement a cellular response are not well-understood. To understand the time-dependent dynamics,we manipulated activity for 2 hrs to induce the process of up or down-scaling and metabolically labelled nascent proteins using BONCAT. We analyzed the newly synthesized proteins that exhibited significant increases or decreases in expression in response to activity manipulations and identified 168 proteins. Then, to obtain a temporal trajectory of the cellular response, we compared the proteins synthesized within 2 and 24 hrs of an activity manipulation. Surprisingly, there was little overlap in the significantly regulated newly synthesized proteins identified in the early- and late-response datasets. There was, however, overlap in the functional categories that are modulated early and late, indicating that within protein function groups, different proteomic choices can be made to effect early and late homeostatic responses.