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LRRTM3 interacts with APP and BACE1 and has variants associating with late-onset Alzheimer's disease (LOAD).

Lincoln S, Allen M, Cox CL, Walker LP, Malphrus K, Qiu Y, Nguyen T, Rowley C, Kouri N, Crook J, Pankratz VS, Younkin S, Younkin L, Carrasquillo M, Zou F, Abdul-Hay SO, Springer W, Sando SB, Aasly JO, Barcikowska M, Wszolek ZK, Lewis JM, Dickson D, Graff-Radford NR, Petersen RC, Eckman E, Younkin SG, Ertekin-Taner N - PLoS ONE (2013)

Bottom Line: Brain mRNA levels of LRRTM3 showed significant correlations with BACE1, CTNNA3 and APP in ∼400 humans, but not in LRRTM3 knock-out mice.These 8 SNPs were genotyped in an independent series (1,258 LOADs and 718 controls) and had significant global and individual MLG associations in the combined dataset (p = 0.02-0.05).Collectively, these results suggest that protein interactions between LRRTM3, APP and BACE1, as well as complex associations between mRNA levels of LRRTM3, CTNNA3, APP and BACE1 in humans might influence APP metabolism and ultimately risk of AD.

View Article: PubMed Central - PubMed

Affiliation: Mayo Clinic Florida, Department of Neuroscience, Jacksonville, Florida, USA.

ABSTRACT
Leucine rich repeat transmembrane protein 3 (LRRTM3) is member of a synaptic protein family. LRRTM3 is a nested gene within α-T catenin (CTNNA3) and resides at the linkage peak for late-onset Alzheimer's disease (LOAD) risk and plasma amyloid β (Aβ) levels. In-vitro knock-down of LRRTM3 was previously shown to decrease secreted Aβ, although the mechanism of this is unclear. In SH-SY5Y cells overexpressing APP and transiently transfected with LRRTM3 alone or with BACE1, we showed that LRRTM3 co-localizes with both APP and BACE1 in early endosomes, where BACE1 processing of APP occurs. Additionally, LRRTM3 co-localizes with APP in primary neuronal cultures from Tg2576 mice transduced with LRRTM3-expressing adeno-associated virus. Moreover, LRRTM3 co-immunoprecipitates with both endogenous APP and overexpressed BACE1, in HEK293T cells transfected with LRRTM3. SH-SY5Y cells with knock-down of LRRTM3 had lower BACE1 and higher CTNNA3 mRNA levels, but no change in APP. Brain mRNA levels of LRRTM3 showed significant correlations with BACE1, CTNNA3 and APP in ∼400 humans, but not in LRRTM3 knock-out mice. Finally, we assessed 69 single nucleotide polymorphisms (SNPs) within and flanking LRRTM3 in 1,567 LOADs and 2,082 controls and identified 8 SNPs within a linkage disequilibrium block encompassing 5'UTR-Intron 1 of LRRTM3 that formed multilocus genotypes (MLG) with suggestive global association with LOAD risk (p = 0.06), and significant individual MLGs. These 8 SNPs were genotyped in an independent series (1,258 LOADs and 718 controls) and had significant global and individual MLG associations in the combined dataset (p = 0.02-0.05). Collectively, these results suggest that protein interactions between LRRTM3, APP and BACE1, as well as complex associations between mRNA levels of LRRTM3, CTNNA3, APP and BACE1 in humans might influence APP metabolism and ultimately risk of AD.

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Expression levels of genes in brains of Lrrtm3 knock-out, heterozygote and wild type mice.Bar graphs depicting mean gene expression levels and error bars representing the standard deviations obtained from the averages of 3 animals per genotypic group where expression levels from each mouse brain is assessed in quadruplicate. Expression values are obtained by the delta Ct method, where geometric mean of HPRT and GAPDH is utilized as the control gene expression values. Average expression values (2?(-delta Ct))x100 were plotted on the y-axis. The three mouse genotypic groups are color-coded as shown in the inset. The genes with expression level measurements are shown in groups, with gene names depicted on the x-axis.
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pone-0064164-g004: Expression levels of genes in brains of Lrrtm3 knock-out, heterozygote and wild type mice.Bar graphs depicting mean gene expression levels and error bars representing the standard deviations obtained from the averages of 3 animals per genotypic group where expression levels from each mouse brain is assessed in quadruplicate. Expression values are obtained by the delta Ct method, where geometric mean of HPRT and GAPDH is utilized as the control gene expression values. Average expression values (2?(-delta Ct))x100 were plotted on the y-axis. The three mouse genotypic groups are color-coded as shown in the inset. The genes with expression level measurements are shown in groups, with gene names depicted on the x-axis.

Mentions: Finally, we assessed endogenous mouse brain expression levels of LRRTM3, BACE1, CTNNA3, APP and the other LRRTMs (LRRTM1, LRRTM2 and LRRTM4) in LRRTM3 knock-out (ko), heterozygote and wild type mice (Figure 4). We observed the expected ∼50% reduction of brain LRRTM3 in the heterozygote and the absence of LRRTM3 in the ko mice (p = 0.04), but there were no differences in the levels of any of the other tested genes at either P4 (Figure 4, Table S3 in File S1) or the later 5.3 month timepoints (data not shown). There were no differences in the P4 mouse brain endogenous Aβ40 or Aβ42 levels of the mice from the three LRRTM3 genotypic groups (data not shown).


LRRTM3 interacts with APP and BACE1 and has variants associating with late-onset Alzheimer's disease (LOAD).

Lincoln S, Allen M, Cox CL, Walker LP, Malphrus K, Qiu Y, Nguyen T, Rowley C, Kouri N, Crook J, Pankratz VS, Younkin S, Younkin L, Carrasquillo M, Zou F, Abdul-Hay SO, Springer W, Sando SB, Aasly JO, Barcikowska M, Wszolek ZK, Lewis JM, Dickson D, Graff-Radford NR, Petersen RC, Eckman E, Younkin SG, Ertekin-Taner N - PLoS ONE (2013)

Expression levels of genes in brains of Lrrtm3 knock-out, heterozygote and wild type mice.Bar graphs depicting mean gene expression levels and error bars representing the standard deviations obtained from the averages of 3 animals per genotypic group where expression levels from each mouse brain is assessed in quadruplicate. Expression values are obtained by the delta Ct method, where geometric mean of HPRT and GAPDH is utilized as the control gene expression values. Average expression values (2?(-delta Ct))x100 were plotted on the y-axis. The three mouse genotypic groups are color-coded as shown in the inset. The genes with expression level measurements are shown in groups, with gene names depicted on the x-axis.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3672107&req=5

pone-0064164-g004: Expression levels of genes in brains of Lrrtm3 knock-out, heterozygote and wild type mice.Bar graphs depicting mean gene expression levels and error bars representing the standard deviations obtained from the averages of 3 animals per genotypic group where expression levels from each mouse brain is assessed in quadruplicate. Expression values are obtained by the delta Ct method, where geometric mean of HPRT and GAPDH is utilized as the control gene expression values. Average expression values (2?(-delta Ct))x100 were plotted on the y-axis. The three mouse genotypic groups are color-coded as shown in the inset. The genes with expression level measurements are shown in groups, with gene names depicted on the x-axis.
Mentions: Finally, we assessed endogenous mouse brain expression levels of LRRTM3, BACE1, CTNNA3, APP and the other LRRTMs (LRRTM1, LRRTM2 and LRRTM4) in LRRTM3 knock-out (ko), heterozygote and wild type mice (Figure 4). We observed the expected ∼50% reduction of brain LRRTM3 in the heterozygote and the absence of LRRTM3 in the ko mice (p = 0.04), but there were no differences in the levels of any of the other tested genes at either P4 (Figure 4, Table S3 in File S1) or the later 5.3 month timepoints (data not shown). There were no differences in the P4 mouse brain endogenous Aβ40 or Aβ42 levels of the mice from the three LRRTM3 genotypic groups (data not shown).

Bottom Line: Brain mRNA levels of LRRTM3 showed significant correlations with BACE1, CTNNA3 and APP in ∼400 humans, but not in LRRTM3 knock-out mice.These 8 SNPs were genotyped in an independent series (1,258 LOADs and 718 controls) and had significant global and individual MLG associations in the combined dataset (p = 0.02-0.05).Collectively, these results suggest that protein interactions between LRRTM3, APP and BACE1, as well as complex associations between mRNA levels of LRRTM3, CTNNA3, APP and BACE1 in humans might influence APP metabolism and ultimately risk of AD.

View Article: PubMed Central - PubMed

Affiliation: Mayo Clinic Florida, Department of Neuroscience, Jacksonville, Florida, USA.

ABSTRACT
Leucine rich repeat transmembrane protein 3 (LRRTM3) is member of a synaptic protein family. LRRTM3 is a nested gene within α-T catenin (CTNNA3) and resides at the linkage peak for late-onset Alzheimer's disease (LOAD) risk and plasma amyloid β (Aβ) levels. In-vitro knock-down of LRRTM3 was previously shown to decrease secreted Aβ, although the mechanism of this is unclear. In SH-SY5Y cells overexpressing APP and transiently transfected with LRRTM3 alone or with BACE1, we showed that LRRTM3 co-localizes with both APP and BACE1 in early endosomes, where BACE1 processing of APP occurs. Additionally, LRRTM3 co-localizes with APP in primary neuronal cultures from Tg2576 mice transduced with LRRTM3-expressing adeno-associated virus. Moreover, LRRTM3 co-immunoprecipitates with both endogenous APP and overexpressed BACE1, in HEK293T cells transfected with LRRTM3. SH-SY5Y cells with knock-down of LRRTM3 had lower BACE1 and higher CTNNA3 mRNA levels, but no change in APP. Brain mRNA levels of LRRTM3 showed significant correlations with BACE1, CTNNA3 and APP in ∼400 humans, but not in LRRTM3 knock-out mice. Finally, we assessed 69 single nucleotide polymorphisms (SNPs) within and flanking LRRTM3 in 1,567 LOADs and 2,082 controls and identified 8 SNPs within a linkage disequilibrium block encompassing 5'UTR-Intron 1 of LRRTM3 that formed multilocus genotypes (MLG) with suggestive global association with LOAD risk (p = 0.06), and significant individual MLGs. These 8 SNPs were genotyped in an independent series (1,258 LOADs and 718 controls) and had significant global and individual MLG associations in the combined dataset (p = 0.02-0.05). Collectively, these results suggest that protein interactions between LRRTM3, APP and BACE1, as well as complex associations between mRNA levels of LRRTM3, CTNNA3, APP and BACE1 in humans might influence APP metabolism and ultimately risk of AD.

Show MeSH
Related in: MedlinePlus