Biochemical and Biophysical Research Communications

Volume 405, Issue 1, 4 February 2011, Pages 96–101

Vimentin binds IRAP and is involved in GLUT4 vesicle trafficking

 Yohko Hirata  Toshio Hosaka  Takeo Iwata c  Chung T.K. Le  Bayasgalan Jambaldorj  Kiyoshi Teshigawara,  Nagakatsu Harada  Hiroshi Sakaue  Tohru Sakai,  Katsuhiko Yoshimoto  Yutaka Nakaya

ABSTRACT

Insulin-responsive aminopeptidase (IRAP) and GLUT4 are two major cargo proteins of GLUT4 storage vesicles (GSVs) that are translocated from a postendosomal storage compartment to the plasma membrane (PM) in response to insulin. The cytoplasmic region of IRAP is reportedly involved in retention of GSVs. In this study, vimentin was identified using the cytoplasmic domain of IRAP as bait. The validity of this interaction was confirmed by pull-down assays and immunoprecipitation in 3T3-L1 adipocytes. In addition, it was shown that GLUT4 translocation to the PM by insulin was decreased in vimentin-depleted adipocytes, presumably due to dispersing GSVs away from the cytoskeleton. These findings suggest that the IRAP binding protein, vimentin, plays an important role in retention of GSVs. The Journal of Medical Investigation Vol. 60 (2013) No. 3.4 p. 197-204

Cysteine string protein 1 (CSP1) modulates insulin sensitivity by attenuating glucose transporter 4 (GLUT4) vesicle docking with the plasma membrane

 Bayasgalan Jambaldorj  Eri Terada  Toshio Hosaka  Yuka Kishuku  Yukiko Tomioka  Kaori Iwashima  Yohko Hirata  Kiyoshi Teshigawara  Chung Thi Kim Le  Tadahiko Nakagawa  Nagakatsu Harada  Tohru Sakai  Hiroshi Sakaue  Toshio Matsumoto  Makoto Funaki  Akira Takahashi  Yutaka Nakaya

ABSTRACT Insulin stimulates glucose transporter 4 (GLUT4) vesicle recruitment from its intracellular storage site to the plasma membrane. Cysteine string protein 1 (CSP1) is a SNARE-binding protein involved in the vesicular trafficking of neurotransmitters and other exocytic processes. In this study, we investigated the involvement of CSP1 in insulin-dependent GLUT4 recruitment in 3T3-L1 adipocytes. Over-expression of wild-type CSP1 led to attenuated insulin-stimulated glucose uptake without any change in GLUT4 content in the plasma membrane, rather it inhibits docking by blocking the association of VAMP2 with syntaxin 4. In contrast, knockdown of CSP1 enhanced insulin-stimulated glucose uptake. The mRNA and protein expression of CSP1 was elevated in 3T3-L1 adipocytes in insulin resistant states caused by high levels of palmitate and chronic insulin exposure. Taken together, the results of this study suggest that CSP1 is involved in insulin resistance by interrupting GLUT4 vesicle docking with the plasma membrane. J. Med. Invest. 60: 197-204, August, 2013