title: Characterization of amyotrophic lateral sclerosis-linked P56S mutation of vesicle-associated membrane protein-associated protein B (VAPB/ALS8).
abstract: The P56S mutation in VAPB (vesicle-associated membrane protein-associated protein B) causes autosomal dominant motoneuronal diseases. Although it was reported that the P56S mutation induces localization shift of VAPB from endoplasmic reticulum (ER) to non-ER compartments, it remains unclear what the physiological function of VAPB is and how the P56S mutation in VAPB causes motoneuronal diseases. Here we demonstrate that overexpression of wild type VAPB (wt-VAPB) promotes unfolded protein response (UPR), which is an ER reaction to suppress accumulation of misfolded proteins, and that small interfering RNA for VAPB attenuates UPR to chemically induced ER stresses, indicating that VAPB is physiologically involved in UPR. The P56S mutation nullifies the function of VAPB to mediate UPR by inhibiting folding of VAPB that results in insolubility and aggregate formation of VAPB in non-ER fractions. Furthermore, we have found that expression of P56S-VAPB inhibits UPR, mediated by endogenous wt-VAPB, by inducing aggregate formation and mislocalization into non-ER fractions of wt-VAPB. Consequently, the P56S mutation in a single allele of the VAPB gene may diminish the activity of VAPB to mediate UPR to less than half the normal level. We thus speculate that the malfunction of VAPB to mediate UPR, caused by the P56S mutation, may contribute to the development of motoneuronal degeneration linked to VAPB/ALS8.
authors.affiliation: Departments of Pharmacology and Anatomy, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan.
authors.forename: Kohsuke
authors.initials: K
authors.lastname: Kanekura
authors.forename: Ikuo
authors.initials: I
authors.lastname: Nishimoto
authors.forename: Sadakazu
authors.initials: S
authors.lastname: Aiso
authors.forename: Masaaki
authors.initials: M
authors.lastname: Matsuoka
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics*; D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D045744:Cell Line, Tumor; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000502:physiology; D008040:Genetic Linkage; D020022:Genetic Predisposition to Disease; D006801:Humans; D051379:Mice; D011392:Proline / Q000235:genetics; D017510:Protein Folding; D012694:Serine / Q000235:genetics; D012995:Solubility; D033921:Vesicular Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology
chemical_list: C496748:VAPB protein, human; D033921:Vesicular Transport Proteins; D012694:Serine; D011392:Proline