Neuronal expression of mint1 and mint2, novel multimodular proteins, in adult murine brain

Increased production and deposition of the 40 -42-amino acid ␤-amyloid peptide (A␤) is believed to be central to the pathogenesis of Alzheimer's disease. A␤ is derived from the amyloid precursor protein (APP), but the mechanisms that regulate APP processing to produce A␤ are not fully understood. X11␣ (also known as munc-18-interacting protein-1 (Mint1)) is a neuronal adaptor protein that binds APP and modulates APP processing in transfected non-neuronal cells. To investigate the in vivo effect of X11␣ on A␤ production in the brain, we created transgenic mice that overexpress X11␣ and crossed these with transgenics harboring a familial Alzheimer's disease mutant APP that produces increased levels of A␤ (APPswe Tg2576 mice). Analyses of A␤ levels in the offspring generated from two separate X11␣ founder mice revealed a significant, approximate 20% decrease in A␤(1-40) in double transgenic mice expressing APPswe/X11␣ compared with APPswe mice. At a key time point in A␤ plaque deposition (8 months old), the number of A␤ plaques was also deceased in APPswe/X11␣ mice. Thus, we report here the first demonstration that X11␣ inhibits A␤ production and deposition in vivo in the brain.One pathological hallmark of Alzheimer's disease is deposition of the 40 -42-amino acid ␤-amyloid peptide (A␤) 1 within the brains of affected individuals. A␤ is derived by proteolytic cleavage from the amyloid precursor protein (APP). APP is a type-1 membrane-spanning protein that contains a large ectodomain and a smaller, intracellular endodomain, and A␤ is derived from sequences that encompass parts of both ecto-and trans-membrane domains. Aberrant APP processing/metabolism leading to increased production and deposition of A␤ is believed to be central to the pathogenesis of Alzheimer's disease (for reviews see Refs. 1 and 2).A number of proteins have now been shown to interact with the APP endodomain, including a variety of phosphotyrosinebinding domain proteins (3, 4). These phosphotyrosine-binding domain proteins comprise the Fe65 and X11 families. Disabled and JNK-interacting proteins and their interactions are mediated via the phosphotyrosine-binding domains and sequences surrounding the YENPTY motif in APP (5-18).One such protein is the neuronal adaptor X11␣, which contains a single, centrally located phosphotyrosine-binding domain through which it binds APP. However, X11␣ also contains a number of other protein-protein interaction domains and via these domains mediates the assembly of multi-protein complexes. Aside from APP family members, X11␣-binding partners identified to date include CASK, munc-18, spinophilin/ neurabin, neurexins, the N-type Ca 2ϩ channel pore-forming ␣ 1B subunit, the kinesin superfamily motor protein KIF17, presenilin 1, and the copper chaperone for superoxide dismutase-1 (19 -30).The binding of X11␣ to APP has now been shown to inhibit A␤ production in transfected non-neuronal cells, although the mechanisms that underlie this effect are not known (16,(31)(32)(33). However, whether it fulfills similar functio...

Section: Resultssupporting

confidence: 86%

The Neuronal Adaptor Protein X11α Reduces Aβ Levels in the Brains of Alzheimer's APPswe Tg2576 Transgenic Mice

Lee

Lau

Perkinton

et al. 2003

“…Myc immunoreactivity was most prominent in cell bodies and proximal dendrites. These findings are similar to those described for expression of endogenous X11␤ in the brain, where it, too, is present in the somatodendritic compartment of a wide variety of neuronal subtypes (5,10,37). Thus, the expression pattern of transgenic X11␤ broadly mimics that of the endogenous protein.…”

Section: Resultssupporting

confidence: 84%

The Neuronal Adaptor Protein X11β Reduces Amyloid β-Protein Levels and Amyloid Plaque Formation in the Brains of Transgenic Mice

Lee¹,

Lau²,

Perkinton

et al. 2004

Accumulation of cerebral amyloid ␤-protein (A␤) is believed to be part of the pathogenic process in Alzheimer's disease. A␤ is derived by proteolytic cleavage from a precursor protein, the amyloid precursor protein (APP). APP is a type-1 membrane-spanning protein, and its carboxyl-terminal intracellular domain binds to X11␤, a neuronal adaptor protein. X11␤ has been shown to inhibit the production of A␤ in transfected non-neuronal cells in culture. However, whether this is also the case in vivo in the brain and whether X11␤ can also inhibit the deposition of A␤ as amyloid plaques is not known. Here we show that transgenic overexpression of X11␤ in neurons leads to a decrease in cerebral A␤ levels in transgenic APPswe Tg2576 mice that are a model of the amyloid pathology of Alzheimer's disease. Moreover, overexpression of X11␤ retards amyloid plaque formation in these APPswe mice. Our findings suggest that modulation of X11␤ function may represent a novel therapeutic approach for preventing the amyloid pathology of Alzheimer's disease.X11␤ (also known as munc-18-interacting protein-2; mint-2) is a neuronal adaptor protein involved in the formation of multiprotein complexes in the brain. To fulfill this function, X11␤ contains a number of protein-protein interaction domains through which it binds specific ligands. These include aminoterminal sequences that bind munc-18 and a novel protein XB51 (1-3), two carboxyl-terminal PDZ domains that bind presenilin-1 (4, 5), neurexins (6), and NF-B/p65 (7), and a centrally located PTB domain that binds to the Alzheimer's disease amyloid precursor protein (APP) 1 (8 -11). APP is a type-1 membrane protein that is proteolytically processed to produce secreted derivatives, and one of these is the 40 -42-amino-acid A␤ peptide that is deposited within amyloid plaques in the brains of patients with Alzheimer's disease.Cleavage of APP to release A␤ involves sequential proteolysis by ␤-secretase (BACE1) and ␥-secretase (presenilin/nicastrin/ Aph-1/Pen-2); alternative cleavage by ␣-secretase within the A␤ sequence precludes A␤ production (12)(13)(14). Aberrant processing of APP leading to the increased production of A␤ is believed to contribute to Alzheimer's disease. In particular, the increased production of the longer A␤(1-42) species is thought to be an early pathogenic event in Alzheimer's disease (13).X11␤ is part of a small family of related proteins that also include X11␣ and X11␥; X11␤ and X11␣ are neuronal (15). Both X11␣ and X11␤ inhibit the production of A␤ in transfected non-neuronal cells (16 -18), and recently, X11␣ has been shown to inhibit the production and deposition of A␤ in the brains of transgenic mice (19). However, similar in vivo transgenic studies have not been performed for X11␤, and this represents a major omission. This is because neurons can process APP to produce A␤ differently from cell lines in culture (20 -23) and because the deposition of A␤ can only be studied properly in vivo in the brain.Likewise, it is important to study the effects of both X11␤ ...

“…7A, GFP-TrkA was mainly localized at the cell surface without NGF treatment and internalized after NGF stimulation, consistent with a previous report (50). In contrast, the majority of Myc-Mint2 colocalized with WGA, suggesting that MycMint2 was mainly localized in the Golgi apparatus, as has been suggested previously (47). Moreover, GFP-TrkA was found to colocalize with Myc-Mint2 and WGA.…”

Section: Identification Of Mint2 As a Potential Binding Partner Of Trsupporting

confidence: 91%

“…There is evidence that Mint1 and Mint2 are enriched in the Golgi apparatus but are also distributed throughout axons and dendrites (28,47). Mints bind to munc-18, a protein essential for synaptic vesicle exocytosis, and to CASK, which is involved in targeting and localization of synaptic membrane proteins (58).…”

Section: Discussionmentioning

confidence: 99%

Interaction of Mint2 with TrkA Is Involved in Regulation of Nerve Growth Factor-induced Neurite Outgrowth

Zhang

Wang

Zhang

et al. 2009

TrkA receptor signaling is essential for nerve growth factor (NGF)-induced survival and differentiation of sensory neurons. To identify possible effectors or regulators of TrkA signaling, yeast two-hybrid screening was performed using the intracellular domain of TrkA as bait. We identified muc18-1-interacting protein 2 (Mint2) as a novel TrkA-binding protein and found that the phosphotyrosine binding domain of Mint2 interacted with TrkA in a phosphorylation-and ligand-independent fashion. Coimmunoprecipitation assays showed that endogenous TrkA interacted with Mint2 in rat tissue homogenates, and immunohistochemical evidence revealed that Mint2 and TrkA colocalized in rat dorsal root ganglion neurons. Furthermore, Mint2 overexpression inhibited NGF-induced neurite outgrowth in both PC12 and cultured dorsal root ganglion neurons, whereas inhibition of Mint2 expression by RNA interference facilitated NGF-induced neurite outgrowth. Moreover, Mint2 was found to promote the retention of TrkA in the Golgi apparatus and inhibit its surface sorting. Taken together, our data provide evidence that Mint2 is a novel TrkA-regulating protein that affects NGF-induced neurite outgrowth, possibly through a mechanism involving retention of TrkA in the Golgi apparatus.