LIS1 is a microtubule‐associated phosphoprotein

Abstract

Lissencephaly, a severe brain malformation, may be caused by mutations in the LIS1 gene. LIS1 encodes a microtubule-associated protein (MAP) that is also part of the enzyme complex, platelet-activating factor acetylhydrolase. LIS1 is also found in a complex with two protein kinases; a T-cell Tat-associated kinase, which contains casein-dependant kinase (CDK) activating kinase (CAK), as well as CAK-inducing activity, and with a spleen protein-tyrosine kinase similar to the catalytic domain of p72syk. As phosphorylation is one of the ways to control cellular localization and protein±protein interactions, we investigated whether LIS1 undergoes this posttranslational modification. Our results demonstrate that LIS1 is a developmentally regulated phosphoprotein. Phosphorylated LIS1 is mainly found in the MAP fraction. Phosphoamino acid analysis revealed that LIS1 is phosphorylated on serine residues. Alkaline phosphatase treatment reduced the number of visible LIS1 isoforms.In-gel assays demonstrate a 50-kDa LIS1 kinase that is enriched in microtubule-associated fractions. In vitro, LIS1 was phosphorylated by protein kinase CKII (casein kinase II), but not many other kinases that were tested. We suggest that LIS1 activity may be regulated by phosphorylation.

LIS1, CLIP-170's Key to the Dynein/Dynactin Pathway

“…19, affinity purified] and monoclonal [no. 210]) were described previously (57,58). Other antibodies were monoclonal anti-p150GLUED (Transduction Laboratories, Lexington, Ky.), anti-cytoplasmic dynein intermediate-chain monoclonal antibody 70.1 (Sigma), human CREST autoimmune antiserum recognizing the centromeric region of chromosomes (a gift from H. Ponstingl, German Cancer Research Center, Heidelberg, Germany), monoclonal anti-␤-tubulin (Zymed Laboratories, Inc., South San Francisco, Calif.), and monoclonal anti-myc 9E10 (22).…”

Regulation of Cytoplasmic Dynein ATPase by Lis1

“…Lis1 reportedly interacts with tubulin and possibly with microtu- bules (Sapir et al, 1999). We reasoned that Lis1 could promote dynein association with microtubules, or alter microtubules themselves, to indirectly increase ATP hydrolysis.…”

“…Lis1 dimerizes through a self-association domain in the N terminus. Lis1 may interact directly with tubulin and/or microtubules (MTs) (Sapir et al, 1999). Although the list of potential Lis1-interacting proteins continues to grow, an important key to understanding the role of Lis1 in development and disease is its association with a multisubunit motor protein, cytoplasmic dynein (Smith et al, 2000;Vallee et al, 2001;Wynshaw-Boris and Gambello, 2001;Gupta et al, 2002;Xiang, 2003), which has critical functions in intracellular transport, mitosis, migration, and nuclear positioning (Banks and Heald, 2001;Dujardin and Vallee, 2002;Tsai and Gleeson, 2005).…”

LIS1—no more no less

“…This interaction and probably others are regulated by phosphorylation. 16 Several of the nud genes (nudA, nudI and nudG) are subunits of cytoplasmic dynein, a microtubule-based motor protein, and nudK is a part of the dynein regulatory complex dynactin. [17][18][19] Recently, it has been shown that the Aspergillus nidulans cytoplasmic dynein heavy chain and NUDF localize to microtubule ends.…”