The effects of low temperatures on intracellular transport of newly synthesized albumin and haptoglobin in rat hepatocytes

Abstract

Isolated rat hepatocytes were pulse-labelled with [35S]methionine at 37 degrees C and subsequently incubated (chased) for different periods of time at different temperatures (37-16 degrees C). The time courses for the secretion of [35S]methionine-labelled albumin and haptoglobin were determined by quantitative immunoprecipitation of the detergent-solubilized cells and of the chase media. Both proteins appeared in the chase medium only after a lag period, the length of which increased markedly with decreasing chase temperature: from about 10 and 20 min at 37 degrees C to about 60 and 120 min at 20 degrees C for albumin and haptoglobin respectively. The rates at which the proteins were externalized after the lag period were also strongly affected by temperature, the half-time for secretion being 20 min at 37 degrees C and 200 min at 20 degrees C for albumin; at 16 degrees C no secretion could be detected after incubation for 270 min. Analysis by subcellular fractionation showed that part of the lag occurred in the endoplasmic reticulum and that the rate of transfer to the Golgi complex was very temperature-dependent. The maximum amount of the two pulse-labelled proteins in Golgi fractions prepared from cells after different times of chase decreased with decreasing incubation temperatures, indicating that the transport from the Golgi complex to the cell surface was less affected by low temperatures than was the transport from the endoplasmic reticulum to the Golgi complex.

Stromal Low Temperature Compartment Derived from the Inner Membrane of the Chloroplast Envelope

“…In animal cells, the block of vesicle transport between the endoplasmic reticulum and the Golgi apparatus is usually observed at a relatively sharp transition in the temperature range between 10 and 20°C, the precise temperature depending on species and cell type (9,18,22,27). In both spinach and pea, the low temperature compartments was greatest at 10 to 12'C, although membrane accumulations between the envelope and the thylakoid were also increased at 4 and 1 8'C compared with 23'C.…”

Differential rates of glycoprotein secretion by isolated rat hepatocytes studied in terms of concanavalin A binding

“…These results are consistent with available data concerning the secretion of plasma proteins during incubation at 20°C. Indeed, haptoglobin is fully blocked in the ER, whereas albumin is blocked in the ER and the Golgi (Fries and Lindstrom, 1986). It would appear that the transport of soluble and transmembrane glycoproteins is not blocked at the same stage at 20"C, since transmembrane proteins such as influenza virus hemagglutinin and vesicular stomatitis virus G protein accumulate only in the trans Golgi network of MDCK or BHK21 cells, respectively (Matlin and Simons, 1983;Griffiths et al, 1985).…”

“…As some steps of intracellular transport are temperature dependent (Matlin and Simons, 1983;Saraste and Kuismanen, 1984;Fries and Lindstrom, 1986), radiolabelled secreted glycoproteins were accumulated by using an incubation temperature of 20 "C to block intracellular traffic; a synchronous release was then induced by shifting the temperature back to 37°C. In both experiments the secretion of albumin, a nonglycosylated protein, was studied in parallel.…”

Sphingolipid transport in eukaryotic cells

“…After synthesis of an SM with two shortened chains, it was found inside transport vesicles [225,226]. Transport depended on cytosolic proteins and ATP, was inhibited by GTPQS, and transport of this SM and of C 6 -NBDŜ M was strongly temperature-dependent with complete inhibition below 10^15³C, the temperature where vesicular tra¤c of proteins is blocked [225,252,256]. Transport of C 6 -NBD^SM was inhibited in mitotic cells [257].…”