D. Banerjee et al., RAPID MOVEMENT OF NEWLY SYNTHESIZED CHICKEN APOLIPOPROTEIN AI TO TRANS-GOLGI NETWORK AND ITS SECRETION IN MADIN-DARBY CANINE KIDNEY-CELLS, Experimental cell research, 235(2), 1997, pp. 334-344
MDCH cells were utilized to study the biosynthesis and secretion of ch
icken apolipoprotein Al: (apoAI), A full-length apoAI cDNA in an eukar
yotic expression vector was transfected into a MDCR-TGG; cell line, ex
pressing a trans-Golgi network. (TGN) marker (TGG), and stable clones
expressing apoAI were selected, Pulse-chase and cell fractionation stu
dies showed that, compared to gp 80 (an endogenous secretory protein),
apoAI was rapidly transported from RER to Golgi complex within 5 min
and released from the Golgi complex to the cell exterior by 30 min. Im
munofluorescence and three-dimensional laser scanning confocal microsc
opy revealed that-at steady state apoAI was predominantly localized in
the TGN. Transferrin uptake experiments showed that apoAI, localized
in the TGN, was derived primarily from biosynthetic and not from endoc
ytic routes. ApoAI was secreted in a nonpolarized manner. We suggest t
hat apoAI stays transiently in the TGN prior to its secretion and that
the major events of apoAI: biosynthesis in vivo and in MDCH cells are
conserved. Possible mechanisms of rapid ER to Golgi transport and TGN
localization of apoAI are discussed. (C) 1997 Academic Press.