sshikano@uic.edu
Research Interests:
Molecular interactions directing the membrane
protein localization
My laboratory is interested in understanding the molecular mechanisms of the membrane protein trafficking. As the human genome sequences have become available, the mutations of genes that cause many human diseases are correlated with abnormal intracellular trafficking. The mechanisms for controlling the protein targeting are therefore of great interest both conceptually and clinically. Currently we focus on identifying and mechanistically characterizing the transport signals on cargo proteins that ‘zipcode’ the surface membrane localization. Our long term goal is to provide a basis for future therapeutic intervention of disorders arising from the protein trafficking defect.Protein sorting is often mediated by short peptidic epitopes, |
|
Dr.
Sojin Shikano, Assistant Professor
PhD, DVM, University ofTokyo
Post Doctoral Fellow
UT Southwestern Medical Center
John Hopkins University
|
|
such as the C-terminal KKXX for endoplasmic reticulum (ER) residential transmembrane proteins and the internal ‘RXR’ signals found in multimeric transmembrane proteins. These signals serve as the recognition signatures for transport machinery proteins that are responsible for retrieval of cargo vesicles back to ER. For cell surface expression of membrane proteins, the export from ER is the first critical step. Earlier it was believed that the cell surface proteins can automatically exit ER by ‘bulk-flow’ mechanism unless they are trapped by ER retention/retrieval machineries as a result of misfolding or misassembly. However, recent works have revealed the presence of specific ‘forward trafficking’ signals that actively mediate ER export in some proteins.
One of the important emerging themes is that a given surface membrane protein may contain multiple different sorting signals, such as ER retention/retrieval and ER export. Such signal organization in a protein permits a molecular mechanism of multiple check points for posttranslational events that include folding, assembly, and modifications. Obviously, the interesting question here will be: “what is the mechanism that organizes multiple different motifs in an individual molecule and eventually confers the proper localization at cell surface?” In order to understand this, the comprehensive approach to the identity of ER export signals is essential. So far, however, most of such signals have been found as results of studies on individual proteins.
We have embarked on a systematic search for the forward trafficking signals in membrane proteins. We developed a gain-of-function screening using the power of yeast genetics, and identified a number of novel peptide signals that direct surface expression of membrane proteins in mammalian cell. These include a group of sequences that conferred surface expression by overriding the ER retention signal through specific interaction with 14-3-3 proteins in a phosphorylation-dependent manner. This would represent a new protein targeting pathway by which the cells respond to the external signals involving phosphorylation. We are currently studying the molecular mechanisms underlying this 14-3-3-mediated surface expression of membrane proteins by genetic and biochemical approach.
Our research interests include:
▪ Screening and functional characterization of novel protein transport signals
▪ Molecular mechanisms for 14-3-3-mediated surface expression
▪ Regulatory mechanisms of ‘RXR’ ER retention/retrieval signal
▪ Signal-induced transport of potassium channels
▪ Utilization of host transport machineries by infectious pathogens
Selected
Publications:
Shikano, S., Bonkobara, M., Zukas, P. K. & Ariizumi, K. (2001) Molecular cloning of a dendritic cell-associated transmembrane protein, DC-HIL, that promotes RGD-dependent adhesion of endothelial cells through recognition of heparan sulfate proteoglycans. J Biol. Chem. 276, 8125-34.
Chung, J. J., Shikano, S., Hanyu, Y. & Li, M. (2002) Functional diversity of protein C-termini: more than zipcoding? Trends Cell Biol. 12, 146-50.
Shikano, S. & Li, M. (2003) Membrane receptor trafficking: Evidence of proximal and distal zones conferred by two independent endoplasmic reticulum localization signals. Proc Natl Acad Sci USA. 100, 5783-88.
Takao, J., Yudate, T., Das, A., Shikano, S., Bonkobara, M., Ariizumi, K. & Cruz, P.D. (2003) Expression of NF-kappaB in epidermis and the relationship between NF-kappaB activation and inhibition. Br J Dermatol. 148, 680-8.
Sun, H., Shikano, S., Xiong, Q. & Li, M. (2004) Function recovery after chemobleaching (FRAC): evidence for activity silent membrane receptors on cell surface. Proc Natl Acad Sci USA. 101, 16964-9.
Coblitz, B., Shikano, S., Wu, M., Gabelli, S.B., Cockrell, L.M., Spieker, M., Hanyu, Y., Fu, H., Amzel, L.M. & Li, M. (2005) C-terminal recognition by 14-3-3 proteins for surface expression of membrane receptors. J Biol Chem. 280, 36263-72.
Shikano, S., Coblitz, B., Sun, H. & Li, M. (2005) Genetic isolation of transport signals directing cell surface expression. Nat Cell Biol. 10, 985-92.
Sato, K., Shikano, S., Xia, G., Takao, J., Chung, J.S., Cruz, P.D., Jr., Xie, X.S. & Ariizumi, K. (2006) Selective expression of vacuolar H(+)-ATPase subunit d2 by particular subsets of dendritic cells among leukocytes. Mol Immunol. 43, 1443-53.
Wu, M., Coblitz, B., Shikano, S., Long, S., Cockrell, L. M., Fu, H. & Li, M. (2006) SWTY-A general peptide probe for homogenous solution binding assay of 14-3-3 proteins. Anal Biochem. 349, 186-96.
Coblitz, B., Shikano, S., Wu, M. & Li, M. (2006) C-terminal binding: an expanded repertoire and function of 14-3-3 proteins. FEBS Lett. 580, 1531-5.
Sun, H., Liu, X., Xiong, Q., Shikano, S. & Li, M. (2006) Chronic inhibition of cardiac kir2.1 and HERG potassium channels by celastrol with dual effects on both ion conductivity and protein trafficking. J Biol Chem. 281, 5877-84.
Shikano, S., Coblitz, B., Wu, M. & Li, M. (2006) 14-3-3 proteins: regulation of ER localization and surface expression of membrane. Trends Cell Biol. 16, 370-5.
Wu, M., Coblitz, B., Shikano, S., Long, S., Spieker, M., Frutos, A.G., Mukhopadhyay, S. & Li, M. (2006) Phospho-specific recognition by 14-3-3 proteins and antibodies monitored by a high throughput label-free optical biosensor. FEBS Lett. 580, 5681-9.
Ma, D., Nakata, T., Zhang, G., Hoshi, T., Li, M. & Shikano, S. (2007) Differential trafficking of carboxyl isoforms of Ca2+-gated (Slo1) potassium channels. FEBS Lett. 6, 1000-8.
Chung, JJ., Okamoto, Y., Coblitz, B., Li M., Qiu, Y., & Shikano, S. (2009) PI3K/Akt signaling-mediated protein surface expression sensed by 14-3-3 interacting motif. FEBS J. 276, 5547-58
Okamoto, Y & Shikano, S. (2011) Phosphorylation-dependent C-terminal binding of 14-3-3 proteins promotes cell surface expression of HIV co-receptor GPR15. J Biol Chem. 286, 7171-81.
|
