Functional Studies Of The Regulatory Proteins Underlying Golgi Plasticity And Dynamics

The Golgi apparatus is a cytoplasmic organelle involved in the processing proteins produced on the ribosomes of the rough endoplasmic reticulum (ER), and sorting and packaging of proteins for transport to a variety of cellular locations. Hence, Golgi is essential for living cells. Since the discovery of the Golgi in 19th century, we have made a great progress in understanding the dynamic behavior and the function of Golgi. The mechanism underlying its assembly processes and function regulation, however, is still cloudy so far.Appearing in 1970s, Yeast Genetics established a good foundation for us biology learners in studying the function and assembly of Golgi in Eukaryotic cells. Moreover, Human Genome Draft which was finished recently also provides us plenty of data in addressing this issue.Yip1p and Yif1p are essential for transport from ER to Golgi stack during the early secretory pathway in budding yeast. Here we report the identification and characterization of human Yif1 (HsYif1). Sequence analysis indicates that HsYif1, like most of the other YIP1 protein family members, contains multiple transmembrane segments. Double immunofluorescence study revealed a co-distribution of HsYif1 with Golgi marker such as GS27. To delineate the function of HsYif1, we conducted a yeast two hybrid assay and identified an interaction between HsYif1 and HsYip1A, a human homolog of yeast Yip1p. In addition, our pull-down assay validates the interaction between HsYif1 and HsYip1A. Moreover, our immunofluorescence study demonstrates the co-distribution of HsYif1 and HsYip1A. Significantly, overexpression of mutant HsYip1A lacked cytosolic region disrupts the localization of HsYif1 to the Golgi, suggesting that HsYip1A specifies the localization of HsYif1 to the Golgi. To elucidate the function of HsYif1, we use deletion mutant HsYif1. Over expression of C terminus of HsYif1 induced breakdown of the Golgi apparatus and accumulation of ER, suggestioning HsYif1 may involves in ER to Golgi transport. Therefore, we conclude that human Yip1A interacts with and determinates the localization of HsYif1 to the Golgi apparatus and HsYif1-HsYip1A complex involved in ER to Golgi transport similar to that of yeast Yif1p-Yip1p complex. While the...