The first stage of 3T3-L1 adipocyte differentiation is growth arrest, which is achieved by contact inhibition at confluence. In growth-arrested confluent 3T3-L1 preadipocytes, α-tubulin acetylation and primary-cilium formation were induced. The blockade of primary-cilium formation by suppressing IFT88 or Kif3a inhibited 3T3-L1 adipocyte differentiation. IGF-1 (IGF-I)-receptor signaling, which is essential for differentiation induction, was sensitized by the formation of a primary cilium in confluent 3T3-L1 preadipocytes. The receptor located in primary cilium was more sensitive to insulin stimulation than that not located in cilia. During cilium formation, insulin receptor substrate 1 (IRS-1), one of the important downstream signaling molecules of the IGF-1 receptor, was recruited to the basal body at which it was phosphorylated on tyrosine by the receptor kinase in cilia. Akt-1, an important signal molecule of the IGF-1 receptor in adipocyte differentiation, was also activated at the basal body. These IGF-1-receptor signaling processes were all inhibited in IFT88- or Kif3a-knockdown cells. Thus, the primary cilium and its basal body formed an organized signaling pathway for the IGF-1 receptor to induce adipocyte differentiation in confluent 3T3-L1 preadipocytes.
High‐silica zeolite Y (FAU) plays a vital role in (petro)chemical industries. However, the slow nucleation and growth kinetics of the high‐silica FAU framework limit its direct synthesis and the improvement of framework SiO2/Al2O3 ratio (SAR). Here, a facile strategy is developed to realize the fast crystallization of high‐silica zeolite Y, which involves the combination of high crystallization temperature, ultra‐stable Y (USY) seeds and efficient organic‐structure directing agent (OSDA). The synthesis can be finished in 5–16 h at 160 °C and with tunable SAR up to 18.2, and the key factors affecting crystallization kinetics and phase purity are elucidated. Moreover, the crystallization process was monitored to reveal the fast crystal growth mechanism. The high‐silica products possess high (hydro)thermal stability and abundant strong acid sites, which endow them excellent catalytic cracking performance, obviously superior to commercial USY.
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