Is Essential for Patterning of Multiple Musculoskeletal Tissues but Dispensable for Tendon Differentiation.

An efficient musculoskeletal system depends on the precise assembly and coordinated growth and function of muscles, skeleton, and tendons. However, the mechanisms that drive integrated musculoskeletal development and coordinated growth and differentiation of each of these tissues are still being uncovered. Epigenetic modifiers have emerged as critical regulators of cell fate differentiation, but so far almost nothing is known about their roles in tendon biology.

FGF signaling patterns cell fate at the interface between tendon and bone.

Tendon and bone are attached by a transitional connective tissue that is morphologically graded from tendinous to osseous and develops from bipotent progenitors that co-express scleraxis (Scx) and Sox9 (Scx/Sox9). Scx/Sox9 progenitors have the potential to differentiate into either tenocytes or chondrocytes, yet the developmental mechanism that spatially resolves their bipotency at the tendon-bone interface during embryogenesis remains unknown. Here, we demonstrate that development of Scx/Sox9 progenitors within the mammalian lower jaw requires FGF signaling.

Differential effects of protein kinase C-eta on apoptosis versus senescence.

Protein kinase C-eta (PKCη) is considered an anti-apoptotic kinase, which promotes cell survival and chemoresistance in several cancers, including breast cancer. We have recently shown that PKCη positively regulates the anti-apoptotic protein Mcl-1 in breast cancer cells, and depletion of PKCη induced proteasomal degradation of Mcl-1. We therefore examined if depletion of PKCη would enhance cellular sensitivity to chemotherapeutic agents.

Development of migrating tendon-bone attachments involves replacement of progenitor populations.

Tendon-bone attachment sites, called entheses, are essential for musculoskeletal function. They are formed embryonically by + progenitors and continue to develop postnatally, utilizing lineage cells. Despite their importance, we lack information on the transition from embryonic to mature enthesis and on the relation between + progenitors and the lineage.

Protein kinase C-eta regulates Mcl-1 level via ERK1.

Protein kinase C (PKC)-eta (PKCη) is a member of the novel category of PKC family. It is overexpressed in breast cancer and was shown to inhibit apoptosis and contribute to chemoresistance. Since the anti-apoptotic Bcl-2 family protein myeloid cell leukemia-1 (Mcl-1) plays an important role in breast cancer cell survival and chemoresistance, we investigated if PKCη regulates Mcl-1 level.

The unique protein kinase Cη: implications for breast cancer (review).

Deregulation of key signal transduction pathways that govern important cellular processes leads to cancer. The development of effective therapeutics for cancer warrants a comprehensive understanding of the signaling pathways that are deregulated in cancer. The protein kinase C (PKC) family has served as an attractive target for cancer therapy for decades owing to its crucial roles in several cellular processes.

Upregulation of PKCη by PKCε and PDK1 involves two distinct mechanisms and promotes breast cancer cell survival.

Background: Protein kinase C (PKC) serves as the receptor for tumor-promoting phorbol esters, which are potent activators of conventional (c) and novel (n) PKCs. We recently showed that these activators induced selective upregulation of PKCη in breast cancer cells. The objective of this study is to understand unique regulation of PKCη and its importance in breast cancer.

Novel regulation of protein kinase C-η.

Protein kinase C (PKC) is the receptor for tumor promoting phorbol esters, which are potent activators of conventional and novel PKCs, but persistent treatment with phorbol esters leads to downregulation of these PKCs. However, PKCη, a novel PKC isozyme, resists downregulation by tumor-promoting phorbol esters, but little is known about how PKCη level is regulated. Phosphorylation and dephosphorylation play an important role in regulating activity and stability of PKCs.

Two faces of protein kinase Cδ: the contrasting roles of PKCδ in cell survival and cell death.

Protein kinase Cδ (PKCδ) is a member of the PKC family that plays a critical role in the regulation of various cellular processes, including cell proliferation, cell death, and tumor promotion. Since the identification that PKCδ is a substrate for caspase-3, there has been overwhelming literature that linked PKCδ with proapoptotic signaling. While PKCδ generally functions as a proapoptotic protein during DNA damage-induced apoptosis, it can act as an antiapoptotic protein during receptor-initiated cell death.