Genetic analysis of synaptotagmin-7 function in synaptic vesicle exocytosis

Anton Maximov, Ye Lao, Hongmei Li, Xiaocheng Chen, Jose Rizo-Rey, Jakob B. Sørensen, Thomas C. Südhof

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

Synaptotagmin-7 is a candidate Ca2+ sensor for exocytosis that is at least partly localized to synapses. Similar to synaptotagmin-1, which functions as a Ca2+ sensor for fast synaptic vesicle (SV) exocytosis, synaptotagmin-7 contains C2A and C2B domains that exhibit Ca2+-dependent phospholipid binding. However, synaptotagmin-7 cannot replace synaptotagmin-1 as a Ca2+ sensor for fast SV exocytosis, raising questions about the physiological significance of its Ca 2+-binding properties. Here, we examine how synaptotagmin-7 binds Ca2+ and test whether this Ca2+ binding regulates Ca 2+-triggered SV exocytosis. We show that the synaptotagmin-7 C 2A domain exhibits a Ca2+-binding mode similar to that of the synaptotagmin-1 C2A domain, suggesting that the synaptotagmin-1 and -7 C2 domains generally employ comparable Ca2+-binding mechanisms. We then generated mutant mice that lack synaptotagmin-7 or contain point mutations inactivating Ca2+ binding either to both C 2 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 ≈70% reduction in synaptotagmin-7 levels, whereas inactivation of Ca2+ 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 Ca2+ binding to the synaptotagmin-7 C2 domains is physiologically important for stabilizing synaptotagmin-7, but that Ca2+ binding by synaptotagmin-7 likely does not regulate SV exocytosis, consistent with a role for synaptotagmin-7 in other forms of Ca2+-dependent synaptic exocytosis.

Original languageEnglish (US)
Pages (from-to)3986-3991
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume105
Issue number10
DOIs
StatePublished - Mar 25 2008

Fingerprint

Synaptotagmins
Synaptic Vesicles
Exocytosis
Synaptotagmin I
Neuronal Plasticity

Keywords

  • Asynchronous release
  • Calcium-binding protein
  • Neurotransmitter release
  • Synaptic plasticity

ASJC Scopus subject areas

  • Genetics
  • General

Cite this

Genetic analysis of synaptotagmin-7 function in synaptic vesicle exocytosis. / Maximov, Anton; Lao, Ye; Li, Hongmei; Chen, Xiaocheng; Rizo-Rey, Jose; Sørensen, Jakob B.; Südhof, Thomas C.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 105, No. 10, 25.03.2008, p. 3986-3991.

Research output: Contribution to journalArticle

Maximov, Anton ; Lao, Ye ; Li, Hongmei ; Chen, Xiaocheng ; Rizo-Rey, Jose ; Sørensen, Jakob B. ; Südhof, Thomas C. / Genetic analysis of synaptotagmin-7 function in synaptic vesicle exocytosis. In: Proceedings of the National Academy of Sciences of the United States of America. 2008 ; Vol. 105, No. 10. pp. 3986-3991.
@article{cc2143f3ee5744ca8289ec9b24149e11,
title = "Genetic analysis of synaptotagmin-7 function in synaptic vesicle exocytosis",
abstract = "Synaptotagmin-7 is a candidate Ca2+ sensor for exocytosis that is at least partly localized to synapses. Similar to synaptotagmin-1, which functions as a Ca2+ sensor for fast synaptic vesicle (SV) exocytosis, synaptotagmin-7 contains C2A and C2B domains that exhibit Ca2+-dependent phospholipid binding. However, synaptotagmin-7 cannot replace synaptotagmin-1 as a Ca2+ sensor for fast SV exocytosis, raising questions about the physiological significance of its Ca 2+-binding properties. Here, we examine how synaptotagmin-7 binds Ca2+ and test whether this Ca2+ binding regulates Ca 2+-triggered SV exocytosis. We show that the synaptotagmin-7 C 2A domain exhibits a Ca2+-binding mode similar to that of the synaptotagmin-1 C2A domain, suggesting that the synaptotagmin-1 and -7 C2 domains generally employ comparable Ca2+-binding mechanisms. We then generated mutant mice that lack synaptotagmin-7 or contain point mutations inactivating Ca2+ binding either to both C 2 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 ≈70{\%} reduction in synaptotagmin-7 levels, whereas inactivation of Ca2+ 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 Ca2+ binding to the synaptotagmin-7 C2 domains is physiologically important for stabilizing synaptotagmin-7, but that Ca2+ binding by synaptotagmin-7 likely does not regulate SV exocytosis, consistent with a role for synaptotagmin-7 in other forms of Ca2+-dependent synaptic exocytosis.",
keywords = "Asynchronous release, Calcium-binding protein, Neurotransmitter release, Synaptic plasticity",
author = "Anton Maximov and Ye Lao and Hongmei Li and Xiaocheng Chen and Jose Rizo-Rey and S{\o}rensen, {Jakob B.} and S{\"u}dhof, {Thomas C.}",
year = "2008",
month = "3",
day = "25",
doi = "10.1073/pnas.0712372105",
language = "English (US)",
volume = "105",
pages = "3986--3991",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
issn = "0027-8424",
number = "10",

}

TY - JOUR

T1 - Genetic analysis of synaptotagmin-7 function in synaptic vesicle exocytosis

AU - Maximov, Anton

AU - Lao, Ye

AU - Li, Hongmei

AU - Chen, Xiaocheng

AU - Rizo-Rey, Jose

AU - Sørensen, Jakob B.

AU - Südhof, Thomas C.

PY - 2008/3/25

Y1 - 2008/3/25

N2 - Synaptotagmin-7 is a candidate Ca2+ sensor for exocytosis that is at least partly localized to synapses. Similar to synaptotagmin-1, which functions as a Ca2+ sensor for fast synaptic vesicle (SV) exocytosis, synaptotagmin-7 contains C2A and C2B domains that exhibit Ca2+-dependent phospholipid binding. However, synaptotagmin-7 cannot replace synaptotagmin-1 as a Ca2+ sensor for fast SV exocytosis, raising questions about the physiological significance of its Ca 2+-binding properties. Here, we examine how synaptotagmin-7 binds Ca2+ and test whether this Ca2+ binding regulates Ca 2+-triggered SV exocytosis. We show that the synaptotagmin-7 C 2A domain exhibits a Ca2+-binding mode similar to that of the synaptotagmin-1 C2A domain, suggesting that the synaptotagmin-1 and -7 C2 domains generally employ comparable Ca2+-binding mechanisms. We then generated mutant mice that lack synaptotagmin-7 or contain point mutations inactivating Ca2+ binding either to both C 2 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 ≈70% reduction in synaptotagmin-7 levels, whereas inactivation of Ca2+ 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 Ca2+ binding to the synaptotagmin-7 C2 domains is physiologically important for stabilizing synaptotagmin-7, but that Ca2+ binding by synaptotagmin-7 likely does not regulate SV exocytosis, consistent with a role for synaptotagmin-7 in other forms of Ca2+-dependent synaptic exocytosis.

AB - Synaptotagmin-7 is a candidate Ca2+ sensor for exocytosis that is at least partly localized to synapses. Similar to synaptotagmin-1, which functions as a Ca2+ sensor for fast synaptic vesicle (SV) exocytosis, synaptotagmin-7 contains C2A and C2B domains that exhibit Ca2+-dependent phospholipid binding. However, synaptotagmin-7 cannot replace synaptotagmin-1 as a Ca2+ sensor for fast SV exocytosis, raising questions about the physiological significance of its Ca 2+-binding properties. Here, we examine how synaptotagmin-7 binds Ca2+ and test whether this Ca2+ binding regulates Ca 2+-triggered SV exocytosis. We show that the synaptotagmin-7 C 2A domain exhibits a Ca2+-binding mode similar to that of the synaptotagmin-1 C2A domain, suggesting that the synaptotagmin-1 and -7 C2 domains generally employ comparable Ca2+-binding mechanisms. We then generated mutant mice that lack synaptotagmin-7 or contain point mutations inactivating Ca2+ binding either to both C 2 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 ≈70% reduction in synaptotagmin-7 levels, whereas inactivation of Ca2+ 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 Ca2+ binding to the synaptotagmin-7 C2 domains is physiologically important for stabilizing synaptotagmin-7, but that Ca2+ binding by synaptotagmin-7 likely does not regulate SV exocytosis, consistent with a role for synaptotagmin-7 in other forms of Ca2+-dependent synaptic exocytosis.

KW - Asynchronous release

KW - Calcium-binding protein

KW - Neurotransmitter release

KW - Synaptic plasticity

UR - http://www.scopus.com/inward/record.url?scp=41649087823&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=41649087823&partnerID=8YFLogxK

U2 - 10.1073/pnas.0712372105

DO - 10.1073/pnas.0712372105

M3 - Article

C2 - 18308933

AN - SCOPUS:41649087823

VL - 105

SP - 3986

EP - 3991

JO - Proceedings of the National Academy of Sciences of the United States of America

JF - Proceedings of the National Academy of Sciences of the United States of America

SN - 0027-8424

IS - 10

ER -