Project Summary: Stroke is a devastating disease affecting millions of Americans. However, most prior stroke drug development programs were unsuccessful for a variety of reasons. One of them may be that the appropriate therapeutic targets remain to be identified. Our recent studies show that massive aggregation of nascent peptide chains (NPCs) may play a role in ischemia-reperfusion injury. NPCs, i.e., newly or partially synthesized polypeptides, are the major source of unfolded proteins and highly prone to toxic aggregation in a normal cell. To avoid toxic aggregation, cellular NPCs must be protected by molecular chaperones. Our latest studies show that brain ischemia damages multiple groups of molecular chaperones, resulting in massive NPC aggregation with the ER, Golgi, and mitochondria structures during reperfusion. The amounts of NPC aggregate-associated organelles increase progressively until delayed neuronal death occurs after brain ischemia. Although our studies strongly support this hypothesis, this remains a largely unsettled issue because no study has ever shown that blocking of NPC aggregation protects the brain from ischemia-reperfusion injury, and molecular target(s) for managing NPC aggregation remain to be identified. Furthermore, it may be vitally important to study the translation ability of these basic science discoveries. We have recently found that the newly developed eIF4E inhibitors have strong anti- NPC aggregation effects and offer robust neuroprotection in animal ischemia models. Aim 1 is designed for proof of concept studies of the novel hypothesis that massive NPC aggregation plays a key role in ischemia-reperfusion injury, and eIF4E is a new and best therapeutic target against NPC aggregation. This new hypothesis has not been tested previously, but is essential to develop new therapeutic strategies against ischemia-reperfusion injury. In this Aim, we will use newly developed initiation inhibitors and several new technologies: (i) to identify the best therapeutic target(s) against massive NPC aggregation; and (ii) to study whether the novel anti-NPC aggregation strategy protects the protein quality control systems, and prevents multiple organelle failure after brain ischemia. Aim 2 proposes studies of the clinical translation ability of the new anti-NPC aggregation strategy. This Aim is based on solid new evidence that postischemic and intraperitoneal injection of eIF4E inhibitors offers robust neuroprotection in animal brain ischemia models. We will initially identify the best therapeutic target(s), and then carry out comprehensive studies of the neuroprotection following the STAIR criteria and the new NIH guideline of Rigor and Reproducibility including: (i) two clinically relevant focal ischemia models; (ii) both male and female, (iii) 3- and 12 month age groups, (iv) post-ischemic treatment, (v) 7- and 28-day endpoints, and (vi) performing thorough molecular, pathological and neurological evaluations. These studies will capture many clinically relevant aspects of the mechanisms and neuroprotection.