Mirk/Dyrk1B controls ventral spinal cord development via Shh pathway

Cross-talk between Mirk/Dyrk1B kinase and Sonic hedgehog (Shh)/Gli pathway affects physiology and pathology. Here, we reveal a novel role for Dyrk1B in regulating ventral progenitor and neuron subtypes in the embryonic chick spinal cord (SC) via the Shh pathway. Using in ovo gain-and-loss-of-function approaches at E2, we report that Dyrk1B affects the proliferation and differentiation of neuronal progenitors at E4 and impacts on apoptosis specifically in the motor neuron (MN) domain. Especially, Dyrk1B overexpression decreases the numbers of ventral progenitors, MNs, and V2a interneurons, while the pharmacological inhibition of endogenous Dyrk1B kinase activity by AZ191 administration increases the numbers of ventral progenitors and MNs. Mechanistically, Dyrk1B overexpression suppresses Shh, Gli2 and Gli3 mRNA levels, while conversely, Shh, Gli2 and Gli3 transcription is increased in the presence of Dyrk1B inhibitor AZ191 or Smoothened agonist SAG. Most importantly, in phenotype rescue experiments, SAG restores the Dyrk1B-mediated dysregulation of ventral progenitors. Further at E6, Dyrk1B affects selectively the medial lateral motor neuron column (LMCm), consistent with the expression of Shh in this region. Collectively, these observations reveal a novel regulatory function of Dyrk1B kinase in suppressing the Shh/Gli pathway and thus affecting ventral subtypes in the developing spinal cord. These data render Dyrk1B a possible therapeutic target for motor neuron diseases.

Dyrk1B overexpression is associated with breast cancer growth and a poor prognosis

Dyrk1B, also called minibrain-related kinase (Mirk), is a member of the dual-specificity tyrosine phosphorylation-regulated kinase (Dyrk)/minibrain family of dual-specificity protein kinases. It is a serine/threonine kinase involved in the regulation of tumor progression and cell proliferation. In this study, the role of Dyrk1B in breast cancer development was investigated. The expression of Dyrk1B was detected by Western blot and immunohistochemistry staining, both of which demonstrated that Dyrk1B was overexpressed in breast cancer tissues and cells. Statistical analysis showed that the extent of Dyrk1B expression was associated with multiple clinicopathologic factors, including tumor size, grade, estrogen receptor status, and Ki-67 expression, and that high expression predicted a poor prognosis. The growth of breast cancer cells was inhibited significantly after knockout of DYRK1B by small interfering RNA (siRNA). Moreover, FoxO1 could be phosphorylated by Dyrk1B, and then FoxO1 was shuttled from the cell nucleus into the cytoplasm, which might be the mechanism of Dyrk1B-mediated survival in breast cancer cells. The results suggest that Dyrk1B plays a key role in the progression of breast cancer and provides a new target for breast cancer therapy.

Role of dual specificity tyrosine-phosphorylation-regulated kinase 1B (Dyrk1B) in S-phase entry of HPV E7 expressing cells from quiescence

The high-risk human papillomavirus (HPV) is the causative agent for cervical cancer. The HPV E7 oncogene promotes S-phase entry from quiescent state in the presence of elevated cell cycle inhibitor p27Kip1, a function that may contribute to carcinogenesis. However, the mechanism by which HPV E7 induces quiescent cells to entry into S-phase is not fully understood. Interestingly, we found that Dyrk1B, a dual-specificity kinase and negative regulator of cell proliferation in quiescent cells, was upregulated in E7 expressing cells. Surprisingly and in contrast to what was previously reported, Dyrk1B played a positive role in S-phase entry of quiescent HPV E7 expressing cells. Mechanistically, Dyrk1B contributed to p27 phosphorylation (at serine 10 and threonine 198), which was important for the proliferation of HPV E7 expressing cells. Moreover, Dyrk1B up-regulated HPV E7. Taken together, our studies uncovered a novel function of Dyrk1B in high-risk HPV E7-mediated cell proliferation. Dyrk1B may serve as a target for therapy in HPV-associated cancers.