Identification and characterization of Noc2 as a potential Rab3B effector protein in epithelial cells.
The Rab3 family small G proteins (Rab3A-D) are involved in the regulated secretory pathway of brain and secretory tissues. Among Rab3-interacting proteins, Rabphilin-3, Rim, and Noc2, all of which contain a conserved Rab3-binding domain (RBD3), are generally recognized Rab3 effector proteins in neurons and secretory cells. Although Rab3B was also detected in epithelial cells, its function remained unknown. We isolated cDNA sequences from human epithelial Caco2-cell mRNA by degenerate RT-PCR based on the conserved amino acid sequence of RBD3. Multiple cDNA clones were identified as encoding Noc2. Northern blot analysis revealed that Noc2 mRNA was expressed not only in secretory tissues but also in epithelial tissues and cell lines. A pull-down assay demonstrated that Noc2 bound to Rab3B in a GTP-dependent manner. When Noc2 was co-expressed with the GTP-bound form of Rab3B, it was recruited from the cytosol to perinuclear membranes. Furthermore, overexpression of Noc2 inhibited the cell-surface transport of basolateral vesicular stomatitis virus glycoprotein. These results suggest that Noc2 functions as a potential Rab3B effector protein in epithelial cells.
Manabe
Shinji
S
Department of Biochemistry, The University of Tokushima, Graduate School of Medicine, Tokushima 770-8503, Japan.
Nishimura
Noriyuki
N
Yamamoto
Yasuyo
Y
Kitamura
Hiroko
H
Morimoto
Shinya
S
Imai
Mayu
M
Nagahiro
Shinji
S
Seino
Susumu
S
Sasaki
Takuya
T
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D018938:Caco-2 Cells; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D018076:DNA, Complementary; D004847:Epithelial Cells / Q000378:metabolism*; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D014018:Tissue Distribution; D014759:Viral Envelope Proteins / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D020692:rab3 GTP-Binding Proteins / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D018076:DNA, Complementary; C028391:G protein, vesicular stomatitis virus; D008562:Membrane Glycoproteins; C120704:RPH3AL protein, human; D014759:Viral Envelope Proteins; C492131:RAB3B protein, human; D020691:rab GTP-Binding Proteins; D020692:rab3 GTP-Binding Proteins