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Characterization of the postsynaptic protein neurogranin in paired cerebrospinal fluid and plasma samples from Alzheimer's disease patients and healthy controls.

Kvartsberg H, Portelius E, Andreasson U, Brinkmalm G, Hellwig K, Lelental N, Kornhuber J, Hansson O, Minthon L, Spitzer P, Maler JM, Zetterberg H, Blennow K, Lewczuk P - Alzheimers Res Ther (2015)

Bottom Line: CSF Ng was significantly increased in AD compared with controls (P < 0.0001), whereas the plasma Ng levels were similar between the groups in both studies.In agreement with previous studies, we show that CSF Ng is significantly increased in AD as compared with healthy controls.The results suggest that CSF Ng, in particular Ng48-76, might reflect the neurodegenerative processes within the brain, indicating a role for Ng as a potential novel clinical biomarker for synaptic function in AD.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, House V3/SU Mölndal, SE-431 80 Mölndal, Sweden ; AlzeCure Foundation, Karolinska Institutet Science Park, Hälsovägen 7, SE-141 57 Huddinge, Sweden.

ABSTRACT

Introduction: Synaptic dysfunction and degeneration are central events in Alzheimer's disease (AD) pathophysiology that are thought to occur early in disease progression. Synaptic pathology may be studied by examining protein biomarkers specific for different synaptic elements. We recently showed that the dendritic protein neurogranin (Ng), including the endogenous Ng peptide 48 to 76 (Ng48-76), is markedly increased in cerebrospinal fluid (CSF) in AD and that Ng48-76 is the dominant peptide in human brain tissue. The aim of this study was to characterize Ng in plasma and CSF using mass spectrometry and to investigate the performance of plasma Ng as an AD biomarker.

Methods: Paired plasma and CSF samples from patients with AD (n = 25) and healthy controls (n = 20) were analyzed in parallel using an immunoassay developed in-house on the Meso Scale Discovery platform and hybrid immunoaffinity-mass spectrometry (HI-MS). A second plasma material from patients with AD (n = 13) and healthy controls (n = 17) was also analyzed with HI-MS. High-resolution mass spectrometry was used for identification of endogenous plasma Ng peptides.

Results: Ng in human plasma is present as several endogenous peptides. Of the 16 endogenous Ng peptides identified, seven were unique for plasma and not detectable in CSF. However, Ng48-76 was not present in plasma. CSF Ng was significantly increased in AD compared with controls (P < 0.0001), whereas the plasma Ng levels were similar between the groups in both studies. Plasma and CSF Ng levels showed no correlation. CSF Ng was stable during storage at -20°C for up to 2 days, and no de novo generation of peptides were detected.

Conclusions: For the first time, to our knowledge, we have identified several endogenous Ng peptides in human plasma. In agreement with previous studies, we show that CSF Ng is significantly increased in AD as compared with healthy controls. The origin of Ng in plasma and its possible use as a biomarker need to be further investigated. The results suggest that CSF Ng, in particular Ng48-76, might reflect the neurodegenerative processes within the brain, indicating a role for Ng as a potential novel clinical biomarker for synaptic function in AD.

No MeSH data available.


Related in: MedlinePlus

Hybrid immunoaffinity-mass spectrometry characterization of plasma neurogranin. (A) Hybrid immunoaffinity-mass spectrometry analysis of human plasma repeatedly detected several short C-terminal peptides. *Peptides found only in plasma and not in cerebrospinal fluid or brain tissue. ‡Nonspecific binding of other plasma proteins to magnetic beads. (B) A cluster of peaks roughly corresponding to the mass of full-length neurogranin (Ng) is present in plasma. *Peak corresponding to the theoretical mass of full-length Ng (7,618 Da). m/z, Mass-to-charge ratio.
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Fig1: Hybrid immunoaffinity-mass spectrometry characterization of plasma neurogranin. (A) Hybrid immunoaffinity-mass spectrometry analysis of human plasma repeatedly detected several short C-terminal peptides. *Peptides found only in plasma and not in cerebrospinal fluid or brain tissue. ‡Nonspecific binding of other plasma proteins to magnetic beads. (B) A cluster of peaks roughly corresponding to the mass of full-length neurogranin (Ng) is present in plasma. *Peak corresponding to the theoretical mass of full-length Ng (7,618 Da). m/z, Mass-to-charge ratio.

Mentions: Plasma Ng was characterized using MALDI-TOF/TOF and high-resolution MS/MS. Several short C-terminal peptides were repeatedly detected by MALDI-TOF/TOF, and 16 of these were independently verified and identified by high-resolution MS/MS (Figure 1A and Table 2). Of these, seven had not previously been detected in brain tissue or CSF [16]. A summary of all Ng peptides that have been identified using MS in plasma, CSF and brain tissue can be found in Additional file 1: Table S1. A cluster of peaks at the m/z ratio corresponding roughly to full-length Ng (theoretical mass: 7,618 Da) was detected (Figure 1B), indicating that the protein most likely is subjected to several posttranslational modifications; however, these have yet to be identified.Figure 1


Characterization of the postsynaptic protein neurogranin in paired cerebrospinal fluid and plasma samples from Alzheimer's disease patients and healthy controls.

Kvartsberg H, Portelius E, Andreasson U, Brinkmalm G, Hellwig K, Lelental N, Kornhuber J, Hansson O, Minthon L, Spitzer P, Maler JM, Zetterberg H, Blennow K, Lewczuk P - Alzheimers Res Ther (2015)

Hybrid immunoaffinity-mass spectrometry characterization of plasma neurogranin. (A) Hybrid immunoaffinity-mass spectrometry analysis of human plasma repeatedly detected several short C-terminal peptides. *Peptides found only in plasma and not in cerebrospinal fluid or brain tissue. ‡Nonspecific binding of other plasma proteins to magnetic beads. (B) A cluster of peaks roughly corresponding to the mass of full-length neurogranin (Ng) is present in plasma. *Peak corresponding to the theoretical mass of full-length Ng (7,618 Da). m/z, Mass-to-charge ratio.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4487851&req=5

Fig1: Hybrid immunoaffinity-mass spectrometry characterization of plasma neurogranin. (A) Hybrid immunoaffinity-mass spectrometry analysis of human plasma repeatedly detected several short C-terminal peptides. *Peptides found only in plasma and not in cerebrospinal fluid or brain tissue. ‡Nonspecific binding of other plasma proteins to magnetic beads. (B) A cluster of peaks roughly corresponding to the mass of full-length neurogranin (Ng) is present in plasma. *Peak corresponding to the theoretical mass of full-length Ng (7,618 Da). m/z, Mass-to-charge ratio.
Mentions: Plasma Ng was characterized using MALDI-TOF/TOF and high-resolution MS/MS. Several short C-terminal peptides were repeatedly detected by MALDI-TOF/TOF, and 16 of these were independently verified and identified by high-resolution MS/MS (Figure 1A and Table 2). Of these, seven had not previously been detected in brain tissue or CSF [16]. A summary of all Ng peptides that have been identified using MS in plasma, CSF and brain tissue can be found in Additional file 1: Table S1. A cluster of peaks at the m/z ratio corresponding roughly to full-length Ng (theoretical mass: 7,618 Da) was detected (Figure 1B), indicating that the protein most likely is subjected to several posttranslational modifications; however, these have yet to be identified.Figure 1

Bottom Line: CSF Ng was significantly increased in AD compared with controls (P < 0.0001), whereas the plasma Ng levels were similar between the groups in both studies.In agreement with previous studies, we show that CSF Ng is significantly increased in AD as compared with healthy controls.The results suggest that CSF Ng, in particular Ng48-76, might reflect the neurodegenerative processes within the brain, indicating a role for Ng as a potential novel clinical biomarker for synaptic function in AD.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, House V3/SU Mölndal, SE-431 80 Mölndal, Sweden ; AlzeCure Foundation, Karolinska Institutet Science Park, Hälsovägen 7, SE-141 57 Huddinge, Sweden.

ABSTRACT

Introduction: Synaptic dysfunction and degeneration are central events in Alzheimer's disease (AD) pathophysiology that are thought to occur early in disease progression. Synaptic pathology may be studied by examining protein biomarkers specific for different synaptic elements. We recently showed that the dendritic protein neurogranin (Ng), including the endogenous Ng peptide 48 to 76 (Ng48-76), is markedly increased in cerebrospinal fluid (CSF) in AD and that Ng48-76 is the dominant peptide in human brain tissue. The aim of this study was to characterize Ng in plasma and CSF using mass spectrometry and to investigate the performance of plasma Ng as an AD biomarker.

Methods: Paired plasma and CSF samples from patients with AD (n = 25) and healthy controls (n = 20) were analyzed in parallel using an immunoassay developed in-house on the Meso Scale Discovery platform and hybrid immunoaffinity-mass spectrometry (HI-MS). A second plasma material from patients with AD (n = 13) and healthy controls (n = 17) was also analyzed with HI-MS. High-resolution mass spectrometry was used for identification of endogenous plasma Ng peptides.

Results: Ng in human plasma is present as several endogenous peptides. Of the 16 endogenous Ng peptides identified, seven were unique for plasma and not detectable in CSF. However, Ng48-76 was not present in plasma. CSF Ng was significantly increased in AD compared with controls (P < 0.0001), whereas the plasma Ng levels were similar between the groups in both studies. Plasma and CSF Ng levels showed no correlation. CSF Ng was stable during storage at -20°C for up to 2 days, and no de novo generation of peptides were detected.

Conclusions: For the first time, to our knowledge, we have identified several endogenous Ng peptides in human plasma. In agreement with previous studies, we show that CSF Ng is significantly increased in AD as compared with healthy controls. The origin of Ng in plasma and its possible use as a biomarker need to be further investigated. The results suggest that CSF Ng, in particular Ng48-76, might reflect the neurodegenerative processes within the brain, indicating a role for Ng as a potential novel clinical biomarker for synaptic function in AD.

No MeSH data available.


Related in: MedlinePlus