International Journal of Molecular Sciences

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Special Issue Information

Dear Colleagues,

The targeting and localization of newly synthesized and imported molecules to their own cellular destinations are fundamental prerequisites for living organisms. Membrane trafficking is responsible for a broad spectrum of cellular functions, including vesicular transport, secretion, biogenesis and the maintenance of organelles, cell division, protein degradation, signal transduction, etc. The impairment of these functions could cause the onset of many diseases; thus, understanding the molecular mechanisms and the regulatory mechanisms of membrane trafficking is important not only to gain knowledge concerning how living organisms function, but also to find new pharmacological targets for a diverse range of diseases. In this Special Issue, we will focus on the physiological functions of the proteins involved in membrane trafficking, especially in the secretory and endosomal pathways. We will also discuss how these pathways could be interconnected and be involved in the onset of many diseases.

Prof. Dr. Satoshi Kametaka
Guest Editor

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Related Special Issue

Published Papers (2 papers)

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Research

20 pages, 4298 KiB

Open AccessArticle

The Role of PKGIα and AMPK Signaling Interplay in the Regulation of Albumin Permeability in Cultured Rat Podocytes

by Patrycja Rachubik, Dorota Rogacka, Irena Audzeyenka, Maria Szrejder, Anna Topolewska, Michał Rychłowski and Agnieszka Piwkowska

Int. J. Mol. Sci. 2023, 24(4), 3952; https://doi.org/10.3390/ijms24043952 - 16 Feb 2023

Viewed by 1711

Abstract

The permeability of the glomerular filtration barrier (GFB) is mainly regulated by podocytes and their foot processes. Protein kinase G type Iα (PKGIα) and adenosine monophosphate-dependent kinase (AMPK) affect the contractile apparatus of podocytes and influence the permeability of the GFB. Therefore, we studied the interplay between PKGIα and AMPK in cultured rat podocytes. The glomerular permeability to albumin and transmembrane FITC-albumin flux decreased in the presence of AMPK activators and increased in the presence of PKG activators. The knockdown of PKGIα or AMPK with small-interfering RNA (siRNA) revealed a mutual interaction between PKGIα and AMPK and influenced podocyte permeability to albumin. Moreover, PKGIα siRNA activated the AMPK-dependent signaling pathway. AMPKα2 siRNA increased basal levels of phosphorylated myosin phosphate target subunit 1 and decreased the phosphorylation of myosin light chain 2. Podocytes that were treated with AMPK or PKG activators were characterized by the different organization of actin filaments within the cell. Our findings suggest that mutual interactions between PKGIα and AMPKα2 regulate the contractile apparatus and permeability of the podocyte monolayer to albumin. Understanding this newly identified molecular mechanism in podocytes provides further insights into the pathogenesis of glomerular disease and novel therapeutic targets for glomerulopathies. Full article

(This article belongs to the Special Issue Molecular Regulatory Mechanisms of Membrane Trafficking 2.0)

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Graphical abstract

15 pages, 5527 KiB

Open AccessArticle

Rab32/38-Dependent and -Independent Transport of Tyrosinase to Melanosomes in B16-F1 Melanoma Cells

by Aya Nishizawa, Yuto Maruta and Mitsunori Fukuda

Int. J. Mol. Sci. 2022, 23(22), 14144; https://doi.org/10.3390/ijms232214144 - 16 Nov 2022

Cited by 3 | Viewed by 2036

Abstract

B16-F1 melanoma cells have often been used as a model to investigate melanogenesis, but the evidence that melanosome biogenesis and transport occur by the same mechanisms in normal melanocytes and B16-F1 cells is insufficient. In this study, we established knockout B16-F1 cells for each of several key factors in melanogenesis, i.e., tyrosinase (Tyr), Hps4, Rab27A, and Rab32·Rab38 (Rab32/38), and then compared their phenotypes with the phenotypes of corresponding mutant mouse melanocyte cell lines, i.e., melan-c, melan-le, melan-ash, and Rab32-deficient melan-cht cells, respectively. The results showed that Tyr and Rab27A are also indispensable for melanin synthesis and peripheral melanosome distribution, respectively, in B16-F1 cells, but that Hps4 or its downstream targets Rab32/38 are not essential for Tyr transport in B16-F1 cells, suggesting the existence of a Rab32/38-independent Tyr transport mechanism in B16-F1 cells. We then performed comprehensive knockdown screening of Rab small GTPases and identified Rab10 and Rab24, previously uncharacterized Rabs in melanocytes, as being involved in Tyr transport under Rab32/38-null conditions. Our findings indicate a difference between the Tyr transport mechanism in melanocytes and B16-F1 cells in terms of Rab32/38-dependency and a limitation in regard to using melanoma cells as a model for melanocytes, especially when investigating the mechanism of endosomal Tyr transport. Full article

(This article belongs to the Special Issue Molecular Regulatory Mechanisms of Membrane Trafficking 2.0)

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