Jaw1/LRMP is associated with the maintenance of Golgi ribbon structure.

Jaw1/LRMP is a membrane protein that is localized to the endoplasmic reticulum and outer nuclear membrane. Previously, we revealed that Jaw1 functions to maintain nuclear shape by interacting with microtubules as a Klarsicht/ANC-1/Syne/homology (KASH) protein. The loss of several KASH proteins causes defects in the position and shape of the Golgi apparatus as well as the nucleus, but the effects of Jaw1 depletion on the Golgi apparatus were poorly understood. Here, we found that siRNA-mediated Jaw1 depletion causes Golgi fragmentation with disordered ribbon structure in the melanoma cell, accompanied by the change in the localization of the Golgi-derived microtubule network. Thus, we suggest that Jaw1 is a novel protein to maintain the Golgi ribbon structure, associated with the microtubule network.

Jaw1/LRMP has a role in maintaining nuclear shape via interaction with SUN proteins.

Jaw1/LRMP is characterized as a Type II integral membrane protein that is localized to endoplasmic reticulum, however, its physiological functions have been poorly understood. An alignment of amino acid sequence of Jaw1 with Klarsicht/ANC-1/Syne/homology (KASH) proteins, outer nuclear membrane proteins, revealed that Jaw1 has a partial homology to the KASH domain. Here, we show that the function of Jaw1 is to maintain nuclear shape in mouse melanoma cell line. The siRNA-mediated knockdown of Jaw1 caused a severe defect in nuclear shape, and the defect was rescued by ectopic expression of siRNA-resistant Jaw1. Since co-immunoprecipitation assay indicates that Jaw1 interacts with Sad-1/UNC-84 (SUN) proteins that are inner nuclear proteins and microtubules, this study suggests that Jaw1 has a role in maintaining nuclear shape via interactions with SUN proteins and microtubules.