Stimulation of albumin endocytosis by cationized ferritin in cultured aortic smooth muscle cells
Anionic microdomains within the aortic smooth muscle cell (SMC) surface glycocalyx represent a potential barrier to the endocytosis of anionic plasma proteins. Cultured SMCs exposed briefly to cationized ferritin (CF) exhibit ultrastructural aggregations of surface anionic sites resulting in intervening areas essentially devoid of anionic charge. Preincubation of cultured aortic medial SMCs with 0.2 mg/ml CF for 1 minute at 37 C resulted in a 4-fold increase in binding and a 13-fold increase in internalization of /sup 125/I-human serum albumin (/sup 125/I-HSA) relative to cells pretreated with native ferritin. When both the CF preincubation and the endocytosis were performed at 4 C, the influence of CF was abolished. Studies at 4 C indicated that CF pretreatment of SMC at 37 C induced high affinity (Kd = 1.5 nM) saturable /sup 125/I-HSA binding, in addition to low-affinity nonsaturable binding. These results were further confirmed by binding competition studies using increasing concentrations of unlabeled HSA. In contrast, low-density lipoprotein, a large anionic molecule, failed to compete with /sup 125/I-HSA for binding sites on CF-pretreated SMCs at either 4 or 37 C. Pulse-chase studies at 37 C indicated that 20-30% of internalized /sup 125/I-HSA was degraded, and 40-50% exocytosed within 24 hours in CF-treated cells. CF pretreatment of the SMCs did not significantly enhance the uptake of /sup 14/C-sucrose as a measure of fluid-phase endocytosis at 30 and 60 minutes. The results of these studies emphasize the potentially important regulatory roles of cell-surface anionic charge distribution and cationic molecules in cellular endocytosis.
- OSTI ID:
- 5692065
- Journal Information:
- Am. J. Pathol.; (United States), Journal Name: Am. J. Pathol.; (United States) Vol. 3; ISSN AJPAA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
AFFINITY
ALBUMINS
AORTA
ARTERIES
BETA DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
BLOOD VESSELS
BODY
CARBON 14 COMPOUNDS
CARDIOVASCULAR SYSTEM
CATIONS
CELL CULTURES
CHARGED PARTICLES
COMPLEXES
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
ENZYMES
FERRITIN
HEMIACETAL DEHYDROGENASES
INTERMEDIATE MASS NUCLEI
IODINE 125
IODINE ISOTOPES
IONS
IRON COMPLEXES
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LACTATE DEHYDROGENASE
METALLOPROTEINS
MUSCLES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
OXIDOREDUCTASES
PROTEINS
RADIOISOTOPES
REACTION KINETICS
TRACER TECHNIQUES
TRANSITION ELEMENT COMPLEXES