Cytoplasmic Dynein Contains a Family of Differentially Expressed Light Chains

Abstract

Cytoplasmic dynein contains a series of accessory proteins associated with the motor containing heavy chains.1 These include three distinct classes of light chains (Mr < approximately 22 000). Here we demonstrate that a previously cloned protein termed rp3 is a bona fide Mr 14 000 light chain component of this microtubule motor complex. The rp3 polypeptide is approximately 55% identical to the Tctex1 dynein light chain, and together, these two proteins define one branch of a diverse family of Mr 14 000 light chains associated with both cytoplasmic and flagellar dyneins. The Tctex1 and rp3 light chains are differentially expressed in various tissues: rp3 is most prevalent in liver and brain cytoplasmic dynein, whereas those tissues contain the least amounts of Tctex1. Immunofluorescence analysis was consistent with the tissue-specific distribution of these proteins and revealed that both rp3 and Tctex1 are present in multiple perinuclear punctate particles. Furthermore, in two cell lines, rp3 was found associated with an elongated structure located in the layer of cytoplasm above the nucleus. Electrophoretic/immunological analysis indicates that there are only single isoforms for these proteins in brain and PC-12 cells, suggesting that alterations in the Mr 14 000 light chains of dynein are achieved at the level of the individual proteins and not by posttranslational modification. Dissection of the cytoplasmic dynein complex revealed that Tctex1, an Mr 8000 LC dimer, and IC74 associate to define a basal-located intermediate chain/light chain complex analogous to that found in flagellar outer arm dynein.

Interaction of the DYNLT (TCTEX1/RP3) Light Chains and the Intermediate Chains Reveals Novel Intersubunit Regulation during Assembly of the Dynein Complex

“…Rat brain and 293T cytosols were fractionated on 5-20% sucrose density gradients as described previously for microtubule affinity purified dynein (19,42). Microtubule pellets were prepared as described previously (42,47).…”

“…For example, pericentrin is transported to the centrosome exclusively by the dynein complexes that contain the light intermediate chain isoform DYNC1LI-1 (23). The DYNLT and DYNLL light chains have been shown to interact with numerous functionally unrelated proteins (3, 14, 15, 24 -27).The two members of the DYNLT family, DYNLT1 (previously called Tctex1) 2 and DYNLT3 (previously called rp3) are found in all cultured cells and adult and fetal tissues so far examined (19,28,29). Unlike the DYNLT isoforms, the expression of the six intermediate chains isoforms are tissue and cell type-specific (18, 30 -32).…”

“…The two members of the DYNLT family, DYNLT1 (previously called Tctex1) 2 and DYNLT3 (previously called rp3) are found in all cultured cells and adult and fetal tissues so far examined (19,28,29). Unlike the DYNLT isoforms, the expression of the six intermediate chains isoforms are tissue and cell type-specific (18, 30 -32).…”

Transport and egress of herpes simplex virus in neurons

“…Cytoplasmic dynein light chain Tctex1 (DYNLT) family, either Tctex1 (DYNLT1) or rp3 (DYNLT3), which share 55% amino acid homology [14], are mutually exclusive in cytoplasmic dynein complexes [23]. Despite their similarities, Tctex1 and rp3 exhibit significant differences in cellular and tissue distributions, as well as in their binding specificities [23][24][25][26][27][28][29][30]. (B) Kinesin-1 consists of two identical heavy chains and two identical light chains.…”

Interactions of Cytoplasmic Dynein Light Chains Tctex-1 and LC8 with the Intermediate Chain IC74

“…The light chains LC8 (10 kDa), Tctex-1 (12.5 kDa), and the intermediate chain IC74 (74 kDa) interact tightly as a subcomplex within the base of the native dynein complex (9). LC8 and Tctex-1 bind to a number of unrelated cargo molecules and are highly conserved among species.…”