Identification and Characterization of a Synaptojanin 2 Splice Isoform Predominantly Expressed in Nerve Terminals

Yasuo Nemoto, Markus R. Wenk, Masami Watanabe, Laurie Daniell, Tomoe Murakami, Niels Ringstad, Hiroshi Yamada, Kohji Takei, Pietro De Camilli

Research output: Contribution to journalArticle

51 Citations (Scopus)

Abstract

We have previously identified synaptojanin 1, a phosphoinositide phosphatase predominantly expressed in the nervous system, and synaptojanin 2, a broadly expressed isoform. Synaptojanin 1 is concentrated in nerve terminals, where it has been implicated in synaptic vesicle recycling and actin function. Synaptojanin 2A is targeted to mitochondria via a PDZ domain-mediated interaction. We have now characterized an alternatively spliced form of synaptojanin 2 that shares several properties with synaptojanin 1. This isoform, synaptojanin 2B, undergoes further alternative splicing to generate synaptojanin 2B1 and 2B2. Both amphiphysin and endophilin, two partners synaptojanin 1, bind synaptojanin 2B2, whereas only amphiphysin binds synaptojanin 2B1. Sequence similar to the endophilin-binding site in synaptojanin 1 is present only in synaptojanin 2B2, and this sequence was capable of affinity purifying endophilin from rat brain. The Sac1 domain of synaptojanin 2 exhibited phosphoinositide phosphatase activity very similar to that of the Sac1 domain of synaptojanin 1. Site-directed mutagenesis further illustrated its functional similarity to the catalytic domain of Sac1 proteins. Antibodies raised against the synaptojanin 2B-specific carboxyl-terminal region identified a 160-kDa protein in brain and testis. Immunofluorescence showed that synaptojanin 2B is localized at nerve terminals in brain and at the spermatid manchette in testis. Active Rac1 GTPase affects the intracellular localization of synaptojanin 2, but not of synaptojanin 1. These results suggest that synaptojanin 2B has a partially overlapping function with synaptojanin 1 in nerve terminals, with additional roles in neurons and other cells including spermatids.

Original languageEnglish
Pages (from-to)41133-41142
Number of pages10
JournalJournal of Biological Chemistry
Volume276
Issue number44
DOIs
Publication statusPublished - Nov 2 2001

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Protein Isoforms
synaptojanin
Brain
Spermatids
Phosphatidylinositols
Phosphoric Monoester Hydrolases
Testis
PDZ Domains
Mutagenesis
Mitochondria
Synaptic Vesicles
GTP Phosphohydrolases
Alternative Splicing
Neurology
Site-Directed Mutagenesis
Nervous System
Neurons
Fluorescent Antibody Technique
Recycling
Rats

ASJC Scopus subject areas

  • Biochemistry

Cite this

Identification and Characterization of a Synaptojanin 2 Splice Isoform Predominantly Expressed in Nerve Terminals. / Nemoto, Yasuo; Wenk, Markus R.; Watanabe, Masami; Daniell, Laurie; Murakami, Tomoe; Ringstad, Niels; Yamada, Hiroshi; Takei, Kohji; De Camilli, Pietro.

In: Journal of Biological Chemistry, Vol. 276, No. 44, 02.11.2001, p. 41133-41142.

Research output: Contribution to journalArticle

Nemoto, Yasuo ; Wenk, Markus R. ; Watanabe, Masami ; Daniell, Laurie ; Murakami, Tomoe ; Ringstad, Niels ; Yamada, Hiroshi ; Takei, Kohji ; De Camilli, Pietro. / Identification and Characterization of a Synaptojanin 2 Splice Isoform Predominantly Expressed in Nerve Terminals. In: Journal of Biological Chemistry. 2001 ; Vol. 276, No. 44. pp. 41133-41142.
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AU - Daniell, Laurie

AU - Murakami, Tomoe

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AU - Yamada, Hiroshi

AU - Takei, Kohji

AU - De Camilli, Pietro

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