The Clathrin Assembly Protein PICALM Is Required for Erythroid Maturation and Transferrin Internalization in Mice

Mai Suzuki,Natsuko Oe,Takaya Abe,Akira Tanimura,Syunsuke Kon,Manabu Fukumoto,Shinya Rai,Hirokazu Tanaka,Kenji Tanabe,Kohji Takei,Itaru Matsumura,Toshio Watanabe,Yuzuru Kanakura,Tsutomu Kume

doi:10.1371/journal.pone.0031854

Abstract

Phosphatidylinositol binding clathrin assembly protein (PICALM), also known as clathrin assembly lymphoid myeloid leukemia protein (CALM), was originally isolated as part of the fusion gene CALM/AF10, which results from the chromosomal translocation t(10;11)(p13;q14). CALM is sufficient to drive clathrin assembly in vitro on lipid monolayers and regulates clathrin-coated budding and the size and shape of the vesicles at the plasma membrane. However, the physiological role of CALM has yet to be elucidated. Here, the role of CALM in vivo was investigated using CALM-deficient mice. CALM-deficient mice exhibited retarded growth in utero and were dwarfed throughout their shortened life-spans. Moreover, CALM-deficient mice suffered from severe anemia, and the maturation and iron content in erythroid precursors were severely impaired. CALM-deficient erythroid cells and embryonic fibroblasts exhibited impaired clathrin-mediated endocytosis of transferrin. These results indicate that CALM is required for erythroid maturation and transferrin internalization in mice.

Highlights

Clathrin-coated vesicles mediate endocytosis of plasma membrane receptors, channels, and transporters, as well as transmembrane proteins and various soluble macromolecules
clathrin assembly lymphoid myeloid leukemia protein (CALM) possesses an AP180 N-terminal homology (ANTH) domain that binds to membrane lipids [9,12,13,14,15] and specific motifs that bind to clathrin and AP-2, which are the primary components of clathrin-coated vesicles [11,14,15]
CALM-deficient mice suffer from severe anemia Many of the tissues in CALM-deficient mice, including liver, kidney and tibia, were smaller compared to wild-type mice (Fig. 2C, E)

Summary

Introduction

Clathrin-coated vesicles mediate endocytosis of plasma membrane receptors, channels, and transporters, as well as transmembrane proteins and various soluble macromolecules. The neuronal homolog of CALM, AP180, has been shown to be sufficient for clathrin lattice assembly on lipid monolayers and for the regulation of clathrin-coated buds and the size and shape of vesicles at the plasma membrane [8,9,10,11]. CALM possesses an AP180 N-terminal homology (ANTH) domain that binds to membrane lipids [9,12,13,14,15] and specific motifs that bind to clathrin and AP-2, which are the primary components of clathrin-coated vesicles [11,14,15]. Cellular depletion of CALM by RNA interference results in the formation of clathrin-coated structures of abnormal size and shape, which suggests that CALM regulates the proper formation of clathrincoated vesicles [11]

Methods

Results

Conclusion