Dynein Light Intermediate Chain: An Essential Subunit That Contributes to Spindle Checkpoint Inactivation

Abstract

The dynein light intermediate chain (LIC) is a subunit unique to the cytoplasmic form of dynein, but how it contributes to dynein function is not fully understood. Previous work has established that the LIC homodimer binds directly to the dynein heavy chain and may mediate the attachment of dynein to centrosomes and other cargoes. Here, we report our characterization of the LIC in Drosophila. Unlike vertebrates, in which two Lic genes encode multiple subunit isoforms, the Drosophila LIC is encoded by a single gene. We determined that the single LIC polypeptide is phosphorylated, and that different phosphoisoforms can assemble into the dynein motor complex. Our mutational analyses demonstrate that, similar to other dynein subunits, the Drosophila LIC is required for zygotic development, germline specification of the oocyte, and mitotic cell division. We show that RNA interference depletion of LIC in Drosophila S2 cells does not block the recruitment of a dynein complex to kinetochores, but it does delay inactivation of Mad2 signaling and mitotic progression. Our observations suggest the LIC contributes to a broad range of dynein functions.

Dlic1 deficiency impairs ciliogenesis of photoreceptors by destabilizing dynein

“…We have now found that the deletion of Dlic1 in mouse leads to the destabilization of DHC, DIC and DLC (Tctex-1) in many mouse tissues or cells, such as retinas and MEFs, but does not affect DLIC2. Our findings support the notion that the assembly of core dynein subunits, including the DHC, DIC and DLIC, is an interdependent process [10]. The discrepancy about the effect of DLIC1 on the stability of the dynein complex or subcomplex between HeLa cells and our Dlic1-deficient mouse cells may result from the different methods used to deplete DLIC1: knockdown by RNAi may not completely eliminate DLIC1 but our Dlic1 −/− mouse is a null mutant.…”

“…Therefore, Dlic1 deficiency-mediated imbalance of cargo transportation between plus-and minus-end directions in cells The role of DLIC proteins in the assembly of the core dynein complex has been controversial. The DLIC protein is required for the stability of both the DHC and DIC in Drosophila and Aspergillus, and is able to stabilize the interaction between DHC and DIC in Aspergillus [10,15]. However, depleting DLIC1 or DLIC2 [11,14] by RNAi in HeLa cells did not affect the protein levels of DHC, DIC and DLC (Tctex-1).…”

“…Loss of the DLIC protein in Drosophila and Aspergillus results in destabilization of both the DHC and DIC and the dynein complex [10,15], although depleting mammalian DLIC1 was reported to have no effects on the stability of dynein subunits or integrity of dynein complex [11,14]. To understand the molecular mechanisms by which the Dlic1 mutation impairs transport function of dynein in photoreceptor cells, we examined the effect of Dlic1 deficiency on dynein in Dlic1 −/− retinas.…”

“…The function of the DLIC protein was first implicated in the control of the mitotic spindle and the assembly of centrioles by the fact that DLIC1, not DLIC2, specifically interacted with pericentrin (PCNT) in Cos-7 cells [7]. Mutations in the gene encoding DLIC or depleting its gene product by RNAi were shown to result in a variety of mitotic defects from yeast to mammals [8][9][10][11]. DLIC1 also participates in intracellular vesicle transport via forming a complex with small GTPases Rab4 and Rab11, respectively [12,13].…”

“…However, the functions of the DLIC subunit in keeping the integrity of dynein and Golgi apparatus and the development of neurons are controversial. It was shown that yeast DLIC and mammalian DLIC1 were not required for the stability of dynein complex [9,11,14], but depletion or loss of DLIC in Drosophila cells and Aspergillus nidulans led to destabilization of DHC and DIC [10,15]. Palmer et al [14] reported that depleting DLIC1 by RNAi in HeLa cells disrupted the Golgi apparatus, but Sivaram et al [11] claimed that it had no effect on the Golgi.…”