Digital fluorescence analysis of trafficking of single endosomes containing low-density lipoprotein in adrenocortical cells: facilitation of centripetal motion by adrenocorticotropic hormone.
Imaging of trafficking of endosomes containing low-density lipoprotein (LDL) is useful to analyze cholesterol transport in adrenocortical cells. At 60 min after the application of fluorescently labeled LDL to adrenocortical cells, individual endosomes containing LDL were demonstrated to undergo frequent switching between forward and reverse movement and immobility. The population of moving endosomes (>or=0.065 microm/s) was approximately 75% in control cells. The remaining endosomes were either slowly moving or temporarily immobile. At 3h after the LDL addition, endosomes were concentrated around the circumference of the cell nuclei. The endosome movement was inhibited by nocodazole, implying that endosomes undergo movement along microtubule networks. Anti-dynein antibodies inhibited the motion of endosomes towards the nucleus, and anti-kinesin antibodies inhibited peripherally directed motion. These results imply that both dynein-like and kinesin-like motor proteins bind to the same endosome, resulting in saltatory movements with centripetal or peripherally directed direction, depending on which motor binds to microtubules. Though the dynein and kinesin motors drive the endosomes very rapidly (microm/s), frequent saltatory motions of single endosomes may induce the very slow net centripetal motion (microm/h).The application of adrenocorticotropic hormone (ACTH) resulted in a facilitation of the centripetal motion of endosomes, resulting in the establishment of the concentration of endosomes around cell nuclei within 1 h.
Department of Biophysics and Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan.
Tetsuya
T
Kimoto
Makoto
M
Yamada
Tomomitsu
T
Ichikawa
Daisaku
D
Honma
Richard J
RJ
Cherry
Ian E G
IE
Morrison
Suguru
S
Kawato
D000302:Adrenal Cortex / Q000166:cytology*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D011992:Endosomes / Q000187:drug effects* / Q000378:metabolism*; D005453:Fluorescence; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D020409:Molecular Motor Proteins / Q000378:metabolism; D009068:Movement / Q000187:drug effects*; D015739:Nocodazole / Q000494:pharmacology
D000906:Antibodies; D008077:Lipoproteins, LDL; D020409:Molecular Motor Proteins; D000324:Adrenocorticotropic Hormone; D015739:Nocodazole; D002118:Calcium