N-terminal splicing extensions of the human MYO1C gene fine-tune the kinetics of the three full-length myosin IC isoforms

Abstract

The gene produces three alternatively spliced isoforms, differing only in their N-terminal regions (NTRs). These isoforms, which exhibit both specific and overlapping nuclear and cytoplasmic functions, have different expression levels and nuclear-cytoplasmic partitioning. To investigate the effect of NTR extensions on the enzymatic behavior of individual isoforms, we overexpressed and purified the three full-length human isoforms from suspension-adapted HEK cells. MYO1C favored the actomyosin closed state (AM), MYO1C populated the actomyosin open state (AM) and AM equally, and MYO1C favored the AM state. Moreover, the full-length constructs isomerized before ADP release, which has not been observed previously in truncated MYO1C constructs. Furthermore, global numerical simulation analysis predicted that MYO1C populated the actomyosin·ADP closed state (AMD) 5-fold more than the actomyosin·ADP open state (AMD) and to a greater degree than MYO1C and MYO1C (4- and 2-fold, respectively). On the basis of a homology model of the 35-amino acid NTR of MYO1C (NTR) docked to the X-ray structure of MYO1C, we predicted that MYO1C NTR residue Arg-21 would engage in a specific interaction with post-relay helix residue Glu-469, which affects the mechanics of the myosin power stroke. In addition, we found that adding the NTR peptide to MYO1C yielded a protein that transiently mimics MYO1C kinetic behavior. By contrast, NTR, which harbors the R21G mutation, was unable to confer MYO1C-like kinetic behavior. Thus, the NTRs affect the specific nucleotide-binding properties of MYO1C isoforms, adding to their kinetic diversity. We propose that this level of fine-tuning within MYO1C broadens its adaptability within cells.

Pentachloropseudilin Inhibits Transforming Growth Factor‐β (TGF‐β) Activity by Accelerating Cell‐Surface Type II TGF‐β Receptor Turnover in Target Cells

“…Moreover,c hanges in IC 50 mayr esult from differential splicing in the myosin motor domain region.I nt he case of human Myo1c, N-terminal splicing extensions exist that can fine-tune the kinetics of the three full-length Myo1c isoforms. [22] Conclusion In this study,w ed emonstrated that the chlorinated phenylpyrrole pentachloropseudilin potently interrupted key transforming growth factor-b-mediated cellular responses, including epithelial to mesenchymal transition ande xtracellular matrix production. The resultsr eveal the potential for this compound and its analogues in anticancer and antifibrosis therapy.…”

“…Moreover, changes in IC 50 may result from differential splicing in the myosin motor domain region. In the case of human Myo1c, N‐terminal splicing extensions exist that can fine‐tune the kinetics of the three full‐length Myo1c isoforms …”

Class I myosins: Highly versatile proteins with specific functions in the immune system

“…These isoforms show several differences in N‐terminal regions. These differences affect the specific nucleotide‐binding properties of Myo1c isoforms, adding diversity to the kinetics of association with actin . One isoform is present in the nucleus and the IQ sites are important for its translocation.…”

“…These differences affect the specific nucleotide-binding properties of Myo1c isoforms, adding diversity to the kinetics of association with actin. 49 One isoform is present in the nucleus and the IQ sites are important for its translocation. Two out of its three IQ domains are needed for Myo1c nuclear transportation.…”

Calcium and Nuclear Signaling in Prostate Cancer

“…The most recent results have implicated it in the prostate cancer cell migration and invasion [ 136 ]. The three isoforms of this protein, including the recently discovered one (A) that is associated with metastatic prostate cancer [ 186 , 187 ]; and the one (B) originally described as the nuclear myosin [ 188 ], differ kinetically, according to the latest work [ 189 ].…”