Decorin inhibits the epidermal growth factor receptor (EGFR) by down-regulating its tyrosine kinase activity, thereby blocking the growth of a variety of transformed cells and tumor xenografts. In this study we provide evidence that decorin directly binds to the EGFR causing its dimerization, internalization, and ultimately its degradation. Using various pharmacological agents to disrupt clathrin-dependent and -independent endocytosis, we demonstrate that decorin evokes a protracted internalization of the EGFR primarily via caveolar-mediated endocytosis. In contrast to EGF, decorin targets the EGFR to caveolae, but not to early or recycling endosomes. Ultimately, however, both EGF-and decorin-induced pathways converge into late endosomes/lysosomes for final degradation. Thus, we have discovered a novel biological mechanism for decorin that could explain its anti-proliferative and anti-oncogenic mode of action.Decorin, the prototypic member of an expanding family of small leucine-rich proteoglycans (1), is implicated in modulating collagen fibrillogenesis (2, 3) and cell growth and survival (4 -8). The mechanism of decorin action has begun to be elucidated by the discovery that decorin interferes with epidermal growth factor receptor (EGFR) 3 signaling (9, 10). Decorin leads to a protracted down-regulation of EGFR tyrosine kinase (11) and other members of the ErbB family of receptor tyrosine kinase (12), and causes an attenuation of the EGFR-mediated mobilization of intracellular calcium (11). Decorin induces expression of the endogenous cyclin-dependent kinase inhibitor p21 WAF1 (13, 14) and a subsequent arrest of the cells in the G 1 phase of the cell cycle (15). These cytostatic effects occur in a wide variety of tumor cell lines (5, 14) and can also affect murine tumor cells (5) and normal human cells, such as endothelial cells (16) and macrophages (17). During quiescence, decorin expression is markedly up-regulated in most normal diploid cells, whereas its expression is nearly abolished in most transformed cells (2, 18 -20). For example, transformation induced by the activating transcription factor-3 and the nuclear v-Src and v-Jun oncoproteins cause a marked suppression of decorin gene expression (21-23). Lack of decorin expression is permissive for tumor development insofar as mice with a targeted ablation of both decorin and the tumor suppressor gene p53, develop lymphomas at accelerated rates as compared with the p53 null animals (24). Consistent with these findings, decorin expression is differentially down-regulated in hepatocellular (25), lung (26), and ovarian (27) carcinomas, and reduced expression of decorin is associated with a poor prognosis in invasive breast carcinoma (28). Finally, adenovirus-mediated gene transfer of decorin causes a significant growth inhibition of various tumors (6, 29), and its de novo expression prevents metastastic spreading in a breast carcinoma model (30).The similarity of the response to decorin in several human cell lines with a diverse histogenetic background and th...

Sleep disorders are highly prevalent in patients with traumatic brain injury (TBI) and can significantly impair cognitive rehabilitation. No proven therapies exist to mitigate the neurocognitive consequences of TBI. We show that mild brain injury in mice causes a persistent inability to maintain wakefulness and decreases orexin neuron activation during wakefulness. We gave mice a dietary supplement of branched-chain amino acids (BCAAs), precursors for de novo glutamate synthesis in the brain. BCAA therapy reinstated activation of orexin neurons and improved wake deficits in mice with mild brain injury. Our data suggest that dietary BCAA intervention, acting in part through orexin, can ameliorate injury-induced sleep disturbances and may facilitate cognitive rehabilitation after brain injury.

SummaryFragmentation of wakefulness and sleep are expected outcomes of advanced aging. We hypothesize that wake neurons develop endoplasmic reticulum dyshomeostasis with aging, in parallel with impaired wakefulness. In this series of experiments, we sought to more fully characterize age-related changes in wakefulness and then, in relevant wake neuronal populations, explore functionality and endoplasmic reticulum homeostasis. We report that old mice show greater sleep/wake transitions in the active period with markedly shortened wake periods, shortened latencies to sleep, and less wake time in the subjective day in response to a novel social encounter. Consistent with sleep/wake instability and reduced social encounter wakefulness, orexinergic and noradrenergic wake neurons in aged mice show reduced c-fos response to wakefulness and endoplasmic reticulum dyshomeostasis with increased nuclear translocation of CHOP and GADD34. We have identified an age-related unfolded protein response injury to and dysfunction of wake neurons. It is anticipated that these changes contribute to sleep/ wake fragmentation and cognitive impairment in aging.