Amylin, a pancreatic peptide, and amyloid-beta peptides (Aβ), a major component of Alzheimer's disease (AD) brain, share similar β-sheet secondary structures, but it is not known whether pancreatic amylin affects amyloid pathogenesis in the AD brain. Using AD mouse models, we investigated the effects of amylin and its clinical analog, pramlintide, on AD pathogenesis. Surprisingly, chronic intraperitoneal (i.p.) injection of AD animals with either amylin or pramlintide reduces the amyloid burden as well as lowers the concentrations of Aβ in the brain. These treatments significantly improve their learning and memory assessed by two behavioral tests, Y maze and Morris water maze. Both amylin and pramlintide treatments increase the concentrations of Aβ1-42 in cerebral spinal fluid (CSF). A single i.p. injection of either peptide also induces a surge of Aβ in the serum, the magnitude of which is proportionate to the amount of Aβ in brain tissue. One intracerebroventricular injection of amylin induces a more significant surge in serum Aβ than one i.p. injection of the peptide. In 330 human plasma samples, a positive association between amylin and Aβ1-42 as well as Aβ1-40 is found only in patients with AD or amnestic mild cognitive impairment. As amylin readily crosses the blood–brain barrier, our study demonstrates that peripheral amylin's action on the central nervous system results in translocation of Aβ from the brain into the CSF and blood that could be an explanation for a positive relationship between amylin and Aβ in blood. As naturally occurring amylin may play a role in regulating Aβ in brain, amylin class peptides may provide a new avenue for both treatment and diagnosis of AD.

Synaptotagmin-7 is a candidate Ca 2؉ sensor for exocytosis that is at least partly localized to synapses. Similar to synaptotagmin-1, which functions as a Ca 2؉ sensor for fast synaptic vesicle (SV) exocytosis, synaptotagmin-7 contains C2A and C2B domains that exhibit Ca 2؉ -dependent phospholipid binding. However, synaptotagmin-7 cannot replace synaptotagmin-1 as a Ca 2؉ sensor for fast SV exocytosis, raising questions about the physiological significance of its Ca 2؉ -binding properties. Here, we examine how synaptotagmin-7 binds Ca 2؉ and test whether this Ca 2؉ binding regulates Ca 2؉ -triggered SV exocytosis. We show that the synaptotagmin-7 C 2A domain exhibits a Ca 2؉ -binding mode similar to that of the synaptotagmin-1 C2A domain, suggesting that the synaptotagmin-1 and -7 C 2 domains generally employ comparable Ca 2؉ -binding mechanisms. We then generated mutant mice that lack synaptotagmin-7 or contain point mutations inactivating Ca 2؉ binding either to both C2 domains of synaptotagmin-7 or only to its C2B domain. Synaptotagmin-7-mutant mice were viable and fertile. Inactivation of Ca 2؉ binding to both C2 domains caused an Ϸ70% reduction in synaptotagmin-7 levels, whereas inactivation of Ca 2؉ binding to only the C2B domain did not alter synaptotagmin-7 levels. The synaptotagmin-7 deletion did not change fast synchronous release, slow asynchronous release, or short-term synaptic plasticity of release of neurotransmitters. Thus, our results show that Ca 2؉ binding to the synaptotagmin-7 C2 domains is physiologically important for stabilizing synaptotagmin-7, but that Ca 2؉ binding by synaptotagmin-7 likely does not regulate SV exocytosis, consistent with a role for synaptotagmin-7 in other forms of Ca 2؉ -dependent synaptic exocytosis.asynchronous release ͉ calcium-binding protein ͉ neurotransmitter release ͉ synaptic plasticity